Baseline Water Quality of Minnesota’s Principal Aquifers ...

Minnesota Pollution Control Agency

Printed with soy-based inks in recycled paper containing at least 10 percent fibers from paper recycled by consumers.

Baseline Water Quality of Minnesota’s Principal Aquifers - Region 1,Northeastern Minnesota

February, 1999

Published by

Minnesota Pollution Control AgencyEnvironmental Outcomes Division

Environmental Monitoring and Analysis SectionGround Water and Toxics Monitoring Unit

520 Lafayette RoadSt. Paul, Minnesota 55155-4194

(651) 296-6300 or (800) 657-3864

Prepared by

Ground Water Monitoring and Assessment Program (GWMAP)

This material may be made available in other formats,such as Braille, large type or audio, upon request.

TDD users call (651) 282-5332

Baseline Water Quality of Minnesota’s Principal Aquifers-Region 1, Northeastern Minnesota January 1999

Ground Water Monitoring and Assessment Program i

Foreword

Ground Water Monitoring and Assessment Program (GWMAP) staff believe the

enclosed report represents a comprehensive study of water quality in the principal aquifers

of MPCA Region 1 in northeastern Minnesota. Information in this report, when used in

conjunction with Baseline Water Quality of Minnesota’s Principal Aquifers (MPCA,

1998a), can be used by water resource managers to identify baseline or background water

quality conditions in areas or aquifers of concern, prioritize ground water problems, and

assist in site decision-making, provided the limitations and assumptions outlined in the

document are understood. Although data have been carefully analyzed, compiled, and

reviewed independently, mistakes are inevitable with a data set this large. If mistakes are

found in this report, please forward them to GWMAP staff. Errata sheets will be prepared

as needed.

The report is divided into four parts. Part I briefly summarizes sample design and

collection. Part II briefly describes analysis methods. Results and discussion are provided

in Part III. Part IV includes a summary of results and recommendations.


Ground Water Monitoring and Assessment Program ii

Abbreviations

CWI - County Well Index

GWMAP - Ground Water Monitoring and Assessment Program

HBV - Health Based Value

HI - Hazard Index

HRL - Health Risk Limit

MCL - Maximum Contaminant Level

MPCA - Minnesota Pollution Control Agency

QA/QC - Quality Assurance/Quality Control

RLs - Reporting Limits

SMCL - Secondary Maximum Contaminant Level

USGS - United States Geological Survey

UTM - Universal Trans Mercator

VOC - Volatile Organic Compound


Ground Water Monitoring and Assessment Program iii

Table of Contents

Foreword iList of Abbreviations iiExecutive Summary v

1. Baseline Design and Implementation 12. Analysis Methods 13. Results and Discussion 2

3.1. Descriptive Summaries 23.2. Group Tests 33.3. Health and Risk 53.4. Aquifers 7

3.4.1. Surficial and Buried Drift Aquifers 93.4.2. Precambrian Aquifers 13

3.4.2.1. Crystalline Aquifers 143.4.2.2. North Shore Volcanics 183.4.2.3. Undifferentiated Precambrian Aquifers 21

3.5. Volatile Organic Compounds 234. Summary and Recommendations 24

4.1. Summary 254.2. Research Recommendations 274.3. Monitoring Needs 27

References 30

Appendix A – Tables 33Appendix B – Figures 34


Ground Water Monitoring and Assessment Program iv


Ground Water Monitoring and Assessment Program v

Executive Summary

In 1995 and 1996, the Minnesota Pollution Control Agency’s (MPCA) Ground

Water Monitoring and Assessment Program (GWMAP) staff sampled 139 primarily

domestic wells in MPCA Region 1, which encompasses northeastern Minnesota. This

sampling effort was part of the statewide baseline assessment (baseline study). The

objectives of the baseline study were to determine water quality in Minnesota’s principal

aquifers, identify chemicals of potential concern to humans, and identify factors affecting

the distribution of chemicals. An important benefit of this study was establishment of

contacts with state and local ground water groups. GWMAP efforts in 1998 and 1999 are

focused on providing information from the baseline study, helping ground water groups

prioritize monitoring efforts, and assisting with sampling and analysis of ground water

monitoring data at the state and local levels.

Samples were collected statewide from a grid at eleven-mile grid node spacings.

One well was sampled from each aquifer group located within a nine-square mile target

area centered on each grid node. Sampling parameters included major cations and anions,

34 trace inorganics, total organic carbon, volatile organic compounds, and field

measurement of dissolved oxygen, oxidation-reduction potential, temperature, pH,

alkalinity, and electrical conductivity. Statewide, 954 wells were sampled from thirty

different aquifer groups.

The hydrology of Region 1 is unique. Water infiltrating through unconsolidated

material (drift) may accumulate and flow along the drift-bedrock interface because of the

low permeability of the bedrock. Wells completed across this interface are considered to

be Precambrian wells, although most of the water may enter the well at the interface.

Despite this, there are significant differences in chemical concentrations of many

chemicals, particularly trace chemicals, between the different Precambrian aquifer groups.

This suggests that water accumulating at the drift-bedrock interface is in contact with

bedrock for sufficient periods of time to develop a chemical signature from the bedrock.

Consequently, different Precambrian groups were compared in this report.

Ground water quality in most aquifers of Region 1 is good. Concentrations of

chemicals in Precambrian aquifers were similar to concentrations in similar aquifers


Ground Water Monitoring and Assessment Program vi

statewide. Concentrations of major cations and anions were lower in surficial and buried

drift aquifers compared to similar aquifers statewide, while concentrations of trace metals

were higher. There appears to be interaction between surficial drift, buried unconfined

aquifers, and underlying bedrock. Processes occurring in the unsaturated zone appear to

have less impact on water quality of these aquifers than in the remainder of the state.

Water quality in Precambrian aquifers varies widely, probably due to wide variability in

residence times. As residence time increases, concentrations of trace elements increase.

Concentrations of most chemicals were well below drinking water criteria, but there were

occasional exceedances of drinking criteria by metals such as beryllium, boron, and

manganese.

The primary research needs for Region 1 include:

• a better understanding of ground water hydrology, particularly mechanisms of

recharge and transport, and determining ground water residence times;

• determining impacts of mineralogy of the different bedrock units on ground

water quality;

• collecting land use information to identify causes of the high occurrence of

VOCs in ground water; and

• a consistent method of classifying bedrock aquifers.

Monitoring needs for Region 1 include:

• collecting additional samples from Precambrian aquifers; and

• collecting an additional 50 samples for VOCs from aquifers most likely to be

impacted by VOCs.


Ground Water Monitoring and Assessment Program vii

The discussion of baseline water quality and chemistry presented in Ground Water

Quality of Minnesota’s Principal Aquifers (MPCA, 1998a) focused on statewide results.

There was no attempt to explain differences in water quality between regions. Since

ground water is largely managed on a regional basis, it is important to identify water

quality issues at the regional level.

This report focuses on MPCA Region 1. Region 1 is located in north central

Minnesota and includes the counties of Aitkin, Carlton, Cook, Itasca, Koochiching, Lake,

and St. Louis (Figure B.1). The regional office is located in Duluth.

The following information needs for Region 1 were identified in Myers et al.,

1992:

• determine water quality of recharge areas;

• determine water quality of surficial and buried sand aquifers in irrigated areas;

and

• evaluate trends in contaminants from stock ponds, feedlots, individual sewage

treatment systems, underground storage tanks, abandoned wells, landfills,

historic dumps, and urban runoff.

Assistance needs were identified in the following areas:

• data interpretation;

• coordination of existing programs; and

• development of local programs.

The baseline study conducted by GWMAP may be used to partly fulfill the

informational needs of determining water quality of recharge areas (provided they are

mapped) and water quality of surficial and buried sand aquifers in irrigated areas. The

baseline study can assist with data interpretation through analysis of the data for the

region, by describing analysis methods useful in local interpretation, and by providing

comparisons between information from the baseline study and other hydrologic

investigations from Region 1.

The purpose of this report is to provide baseline water quality information for

Region 1. Comparisons are made between water quality in the principal aquifers of Region

1 to that in the remainder of the state. Significant differences in ground water quality


Ground Water Monitoring and Assessment Program viii

between Region 1 and the statewide data were determined, factors contributing to these

differences were identified, and potential health implications were investigated. NOTE :

Water quality is a relative term which may have multiple meanings. In this report,

water quality typically refers to water chemistry. Specific instances occur where

water quality relates to potential effects on humans consuming ground water or

general quality of water. The reader should be aware of these different applications

of water quality


Ground Water Monitoring and Assessment Program 1

1. Baseline Design and Implementation

Design and implementation of the baseline study are described in Myers et al.

(1991) and MPCA (1994, 1995, and 1998a). A systematic grid design was implemented,

with sampling nodes spaced at eleven mile intervals. All major aquifers with a suitable

domestic well located within a nine square mile area centered on each grid node were

sampled. The County Well Index (CWI) (Wahl and Tipping, 1991) was used to provide

information on wells within the sampling area. CWI aquifer codes are summarized in

Table A.1. Wells were purged until stabilization criteria were met. Sampling parameters

included field parameters (dissolved oxygen, oxidation-reduction potential, pH,

temperature, electrical conductivity, and alkalinity) major cations and anions, volatile

organic compounds (VOCs), total organic carbon, and 34 trace inorganic chemicals.

Tritium and pesticides were sampled in selected wells. Samples were not filtered.

Rigorous analysis of the data was conducted. Sampling and analysis methods are

described in MPCA 1996 and 1998b, respectively. Sample locations, by aquifer, are

illustrated in Figures B.2 through B.6 for Precambrian crystalline, North Shore Volcanics,

Precambrian undifferentiated, surficial drift and buried drift aquifers, respectively.

Sampling is summarized by aquifer in Table A.1 and for all data in Table A.2.

2. Analysis Methods

Quality assurance/quality control analysis of the data are reported in MPCA

(1998a). Data analysis consisted of

• establishing descriptive statistics (mean, median, minimum, etc.) for each

parameter and each aquifer group;

• conducting hypothesis tests between aquifer groups;

• conducting factor analysis related to the distribution of chemicals in the

principal aquifer groups; and

• conducting an analysis of health and risk.

Methods used in conducting these analyses are described in MPCA (1998b).

3. Results and Discussion



Results are separated into

• descriptive statistics;

• group (hypothesis) tests;

• health and risk;

• discussions for individual aquifer groups; and

• discussions for individual chemicals and chemical parameters.

3.1. Descriptive Summaries

Descriptive statistics include the number of samples, number of censored samples

(samples below the maximum reporting limit), the type of distribution for the data, and the

mean, upper 95th percent confidence limit of the mean, median, 90th or 95th percentile,

minimum, and maximum concentrations. Results are summarized in Tables A.3 through

A.14 for the twelve aquifer groups sampled in Region 1. All concentrations are in ug/L

(ppb) except for Eh (mV), temperature (oC), pH (negative log of the hydrogen ion

concentration), and specific conductivity (umhos/cm). Sample sizes for the Mount Simon-

Hinckley (CMSH), Fond du Lac (PMFL), Hinckley (PMHN), Biwabik Iron Formation

(PEBI), Precambrian undifferentiated (PMUU), and Duluth Complex (PMDC) aquifer

groups were small and no further discussion of these is presented in this section.

Examples of how to use information from Tables A.3 through A.14 in site

applications are provided in MPCA, 1998a. To use these data in site applications, the

coefficients presented in Tables A.15 and A.16 will be needed. Mean and median

concentrations are considered to represent background concentrations with which

site or other local water quality information can be compared. Upper 95th percent

confidence limits and 90th or 95th percentiles represent extremes in the distribution for a

chemical. The distribution of a chemical indicates whether concentrations need to be log-

transformed and whether concentrations below the detection limit will be encountered

during subsequent sampling.

3.2. Group Tests



Group tests are statistical tests which compare concentrations of a chemical or

parameter in one group with concentrations in another group or groups. A group might

be month of sampling, for example, and a group test might explore potential differences in

concentrations of a chemical such as nitrate between two or more months. Concentrations

of sampled chemicals and chemical parameters were compared between different aquifer

groups.

Concentrations of many chemicals differed between different aquifer groups.

Median chemical concentrations were compared between the crystalline Precambrian

(PCCR), North Shore Volcanics (PMNS), undifferentiated Precambrian (PMUD), buried

confined drift (QBAA), buried unconfined drift (QBUA), and surficial drift (QWTA)

aquifer groups. Results are summarized in Table A.17. P-values are included for each

chemical. The p-value indicates the probability that median concentrations between

aquifers are equal. Median concentrations are given in ug/L (except for Eh, redox, pH,

temperature, and specific conductance). Specific aquifers which differed in concentration

are not indicated in Table A.17.

Different median concentrations were observed for many chemicals. Some of

these differences will be discussed in greater detail in the section for individual aquifers,

but the primary conclusions are summarized below.

1. Concentrations of many trace inorganic chemicals, particularly the heavy metals, were

greater in the Precambrian aquifers compared to the Quaternary aquifers.

Concentrations of alkalinity, barium, calcium, silicate, and phosphorus were greater in

the Quaternary aquifers compared to the Precambrian aquifers.

2. Elevated concentrations of aluminum, antimony, boron, fluoride and sodium occurred

in the PMNS aquifer group. Concentrations of chloride, beryllium, zinc, sodium, and

silver were also greatest in the PMNS group, but there were no statistical differences

in concentrations of these chemicals compared to other groups. The chemical

signature in PMNS wells indicates the importance of parent material on water quality.

3. Eh and concentrations of dissolved oxygen, strontium, lead, potassium, total organic

carbon, and chloride were greatest in the PCCR aquifer group, although only dissolved

oxygen and strontium showed statistically different concentrations compared to other



groups. Water quality of the PCCR group shows impacts from parent material and

recharge. Many of these aquifers may be fractured and close to the land surface,

resulting in elevated Eh and concentrations of dissolved oxygen and organic carbon.

4. Concentrations of most chemicals in the PMUD aquifer group were intermediate

between other Precambrian aquifers and Quaternary aquifers. This makes sense, since

there are potentially many different types of parent material which comprise these

aquifers.

5. Concentrations of barium, alkalinity, and arsenic were greatest in the Quaternary

buried, artesian aquifer group. Water quality in this group is strongly influenced by

parent material and residence time. Concentrations of most chemicals in buried,

unconfined Quaternary aquifers are similar to the buried artesian aquifers, as would be

expected since both aquifer groups are found in similar parent material. Residence

time, however, appears to have an impact on water quality in these aquifers, since

concentrations of calcium are lower, while concentrations of potassium, sodium,

chloride, and sulfate are greater in the buried artesian aquifers. Residence times in

buried artesian aquifers should be significantly greater compared to buried unconfined

aquifers.

6. Water quality of water table aquifers (QWTA) is not typical of statewide water quality

in these aquifers. Concentrations of aluminum, iron, and sulfate are greater than the

buried Quaternary aquifers, while Eh is lower. These data suggest interactions with

parent material, but also suggest that aquifers classified as QWTA in this region of the

state are not as responsive to processes occurring in the vadose zone as QWTA

aquifers in other parts of the state.

The hydrology of Region 1 is unique because Precambrian bedrock underlies the

entire region, it is often close to the land surface, and it is relatively impermeable.

Consequently, water moving through the unsaturated zone may only slowly penetrate

underlying bedrock. Water may accumulate and move along the interface between the

unconsolidated (drift) deposits and bedrock. Wells drilled across the interface intercept

this water. If water within these wells reflects inputs from the unsaturated zone, there

should be no differences in water quality of buried Quaternary and Precambrian bedrock



aquifers. Table A.18 compares concentrations in buried Quaternary and Precambrian

bedrock aquifers. It is apparent that water quality differs for many chemicals.

Concentrations of magnesium, bicarbonate (alkalinity), calcium, and potassium were lower

in Precambrian aquifers, while concentrations of aluminum, antimony, beryllium, boron,

cesium, copper, and lead were greater in Precambrian aquifers. Consequently, water is in

contact with bedrock for sufficient lengths of time to develop a chemical signature from

the bedrock. Ground water from Precambrian bedrock is dominated by calcium,

magnesium, and bicarbonate, which is reflective of inputs from the unsaturated zone. The

results support the hypothesis that water percolates through the unsaturated zone,

accumulates at the bedrock-drift interface, and moves sufficiently slow along this interface

to develop a chemical signature from ground water.

3.3. Health and Risk

Drinking water criteria for individual chemicals are summarized in Table A.19. The

Health Risk Limit (HRL) and Health-Based Value (HBV) are health-based criteria. HRLs

are defined in the following manner: HRLs are promulgated concentrations of a ground

water contaminant, in ug/L, which estimates the long-term exposure level which is

unlikely to result in deleterious effects to humans. HRLs strictly incorporate factors

related to human health (Minn. R., Pts. 4717.7100 to 4717.7800). HBVs have a similar

definition, with the exception that they are not promulgated and have not undergone

rigorous external peer review. Drinking water criteria are calculated based on a standard

adult (70 kg) ingestion rate of two liters of water per day. Uncertainty and other exposure

pathways, such as showering, cooking, and inhalation of water vapor, are addressed

through the use of safety factors. Lifetime exposure is assumed to apply to baseline data,

since the sampled wells are used for domestic supply. Maximum Contaminant Levels

(MCLs) and Secondary Maximum Contaminant Levels (SMCLs) are not strictly health-

based and may include factors such as treatability.

The number and percent of samples exceeding health-based ground water drinking

criteria are summarized in Tables A.20 and A.21, respectively. In anticipation of a

change in the HRL for manganese from 100 ug/L to a value of 1000 ug/L or greater,



the drinking criteria for manganese used in this report is modified from the HRL

(MDH, 1997). Sample size was not sufficient for the Mt. Simon-Hickley (CMSH) and

several of the Precambrian aquifer groups (PCUU, PEBI, PMDC, PMFL, and PMHN) to

provide meaningful results. No chemical appeared to represent a significant potential risk

in any aquifer, although the single sample for the Duluth Complex group exceeded the

HRL for beryllium. Boron and beryllium showed a relatively high frequency of exceeding

drinking criteria in Precambrian aquifers, particularly the North Shore Volcanic group.

Two percent of samples exceeded the HRL for boron in buried artesian drift aquifers, but

this is less than half the statewide exceedance rate of 7.7 percent. Arsenic, manganese,

and selenium are other chemicals which exceeded their HRL one time in Precambrian

aquifers.

The number and percent of samples exceeding non-health-based ground water

drinking criteria are summarized in Tables A.22 and A.23, respectively. Non-health-based

drinking criteria include chemicals with a Maximum Contaminant Level (MCL) or

Secondary Maximum Contaminant Level (SMCL). Iron exceeded its SMCL in 38, 42, 50,

52, 58, and 62 percent of the sampled wells in the PCCR, PMNS, PMUD, QBAA,

QBUA, and QWTA aquifer groups, respectively. Aluminum exceeded its SMCL in 31,

50, 10, 15, 0, and 24 percent of wells sampled in the PCCR, PMNS, PMUD, QBAA,

QBUA, and QWTA aquifer groups, respectively. The incidence of other exceedances was

low.

Some chemicals have the same toxic endpoint. For example, Table A.18 indicates

that barium and nitrate both affect the cardiovascular/blood system. A useful calculation

is to estimate the probability that chemicals with the same endpoint will exceed drinking

water criteria. To make this calculation, a hazard index (HI) is used to add the

contribution of each chemical with similar endpoints

[HIendpoint = Cchemical 1/HRLchemcial1 + Cchemical 2/HRLchemcial2 + ... + Cchemical n/HRLchemcialn]

where C represents the concentration (ug/L) of a chemical. If the HI exceeds 1.0 in an

individual well, further investigation is recommended to evaluate the potential factors

controlling chemical concentrations and the validity of the exposure assumptions. These



calculations were not made for this report, primarily because there are a limited number of

samples for all aquifers except the buried drift. The calculations would therefore be

potentially misleading. These calculations were made for statewide data and are reported

in MPCA, 1998a.

3.4. Aquifers

The hydrology and geology of Region 1 is described in numerous reports, although

there is no specific report which encompasses the entire area. The Hydrologic

Investigations Reports for the Big Fork River (Lindholm et al., 1976), Little Fork River

(Helgesen et al., 1976), St. Louis River (Lindholm et al., 1979), Rainy Lake (Ericson et

al., 1976), and Lake Superior (Olcott et al., 1978) watersheds provide information about

climate, the water budget, surface water, and ground water. Precipitation across the

region varies from about 30 inches in the east to 24 inches in the west. Annual runoff to

surface rivers (ground water recharge) varies from more than 11 inches in the east to less

than 6.5 inches in the west. Annual recharge to surficial aquifers may be greater than

these amounts and but will vary widely with annual precipitation. Most of the major rivers

in the region are gaining streams in that they have a baseflow component (ground water

discharges to them).

The hydrogeology of Region 1 is dominated by Precambrian bedrock geology in

two ways. First, Precambrian rocks form an impermeable surface which water does not

penetrate, except in locations where there are fractures. Consequently, water infiltrating

through the soil zone reaches this impermeable surface and then travels laterally along the

interface between the bedrock and the unconsolidated Quaternary deposits. Wells are

often drilled across this interface and into the underlying Precambrian bedrock. The

portion of the well completed in the bedrock acts primarily as a storage basin, while water

enters a well at the interface. Some aquifers may occur within the numerous and irregular

fractured flow zones of the North Shore Volcanic Group and, to a lesser extent, other

crystalline rocks. These flow systems are independent of each other. Second, the

mineralogy of the different bedrock formations is highly variable. Consequently, if ground

water is in contact with bedrock for a sufficient length of time, the ground water will have



a chemical signature reflective of the bedrock. This was observed and discussed in

Section 3.2. Consequently, a discussion of ground water quality from different bedrock

units is appropriate, even if water entering a well is moving along the bedrock-drift

interface. Ground water with long residence times will vary considerably in response to

mineralogical differences.

Sedimentary bedrock deposits are relatively unimportant, constituting aquifers only

in the extreme western and southern portions of the region. Glacial and lacustrine

deposits vary widely in thickness. These deposits are absent in the eastern portion of the

region but may be over 100 feet thick in the western and southern portions. Most surficial

deposits consist of fine-grained lake sediments, peat, and ground moraine. Sand and

gravel deposits occur in bedrock valleys, as beach ridges, at the interface between tills, and

in the extreme southern part of the region, as outwash. Cretaceous bedrock deposits are

unimportant hydrologically within the region.

Ground water originates as precipitation which percolates through the soil and

vadose zone and into the saturated zone (ground water). Most recharge originates in

spring following snowmelt and prior to plant growth, but locations where bedrock is close

to the land surface and near-surface fractured bedrock systems are likely to be responsive

to larger precipitation events during the summer and autumn. There is little information

indicating rates of recharge to the different aquifers in the study area. In areas with

sufficient thickness of overlying glacial deposits, the water table reflects, in a subdued

way, surface topography. Ground water flow is controlled by local factors such as

topography, extent of fracturing, and permeability of glacial deposits. Most flow systems

are local, with discharge occurring to the numerous lakes, streams, and rivers in the

region.

Because ground water systems are generally local, research has focused on specific

geographic areas. There has been no attempt to describe regional ground water resources,

but because of the variability in aquifer parent material and limited demand on ground

water as a source of water for industrial and municipal use, the value of regional analysis

may be questionable. Objectives of regional analysis may therefore focus on differences in

water quality within aquifers from the same parent material and identification of potential



ground water quality problems. The aquifers considered in this report include those

associated with Precambrian crystalline, Precambrian undifferentiated, North Shore

Volcanic, buried Quaternary, and surficial Quaternary deposits.

3.4.1. Surficial and Buried Drift Aquifers

Well-sorted sand and gravel were deposited as beach ridges in glacial lakes, in

bedrock valleys, and as outwash plains by advancing and retreating glaciers. Outwash is

limited to the southern portion of the study area, while beach ridge deposits are most

common in the western part of the study area. Deposits located in bedrock valleys are

scattered throughout the region, except in the northeastern third where bedrock is near the

land surface. Sand and gravel deposits are typically less than 30 feet thick and have

limited potential supply for high capacity uses, but they yield sufficient quantities for

domestic use. Beach ridge deposits are generally less than 10 feet thick, while alluvial

deposits may be as much as 100 feet thick. The scattered distribution of surficial aquifers

is evident in Figure B.6, which illustrates the distribution of wells sampled in Region 1.

These aquifers are vulnerable to contamination from human activity at the land surface.

Hydrologic information, including climatic data and both surface and ground water data,

can be found in the USGS watershed reports for the area (Lindholm et al., 1976; Helgesen

et al., 1976; Lindholm et al., 1979; Ericson et al., 1976; and Olcott et al., 1978).

Using the County Well Index (CWI) nomenclature, the surficial drift group is

comprised of water-table wells (QWTA) while the buried drift group is comprised of both

artesian (QBAA) and unconfined (QBUA) aquifers. QWTA aquifers have less than 10

feet of confining material between the land surface and well screen. There was no attempt

to identify the extent of confinement, depths of well screen, and depth to the water table in

the wells sampled as part of the baseline analysis.

Water quality information for buried and surficial drift aquifer groups of Region 1

is illustrated in Tables A.12 through A.14. These groups have similar concentrations of

dissolved oxygen and similar redox potentials (Eh). Concentrations of total dissolved

solids are lower in the surficial aquifer group than in the buried group, as would be

expected, but concentrations of iron and manganese were greater in the surficial group.



The water quality of surficial drift aquifers in Region 1 differs dramatically

compared to similar aquifers in other areas of the state. The greatest differences were for

alkalinity, antimony, barium, calcium, chloride, magnesium, manganese, specific

conductance, total dissolved solids, and total phosphorus, which were less in Region 1,

and for aluminum and sulfate, which were greater. Water quality of buried aquifers also

differs dramatically with buried aquifers in the remainder of the state. Concentrations of

most chemicals were lower in buried aquifers in Region 1 compared to similar aquifers

statewide. Concentrations of most chemicals were similar between surficial and buried

sand and gravel aquifers within Region 1. In addition, concentrations of alkalinity, boron,

dissolved oxygen, potassium, and sodium were correlated with well depth. The results

suggest confining deposits may be leaky or buried aquifers have short residence times

which results in minimal dissolution of parent material.

Water quality information for surficial and buried drift aquifers in Region 1 is

illustrated in Table A.24 for several different studies. The data indicate GWMAP data

falls within the range of data for most chemicals, but concentrations of boron and sulfate

were lower and iron higher for the GWMAP data. The greatest concentrations of

dissolved solids were observed in the studies by Lindholm et al. (1976) and Helgeson et al.

(1978), which corresponds with the western portion of the study area. Concentrations of

calcium, magnesium, and bicarbonate increase to the west. These results suggest parent

materials comprising the aquifers differs between the eastern and western portions of the

study area. This may be a cause of the large variability in chemical concentrations within

individual CWI aquifer groups for Quaternary deposits.

Water quality of drift aquifers in Region 1 is generally very good. Drinking water

criteria for beryllium, boron, manganese, aluminum, iron, and lead were exceeded in at

least one sample from drift aquifers. Each of these chemicals is discussed below.

Beryllium

The HRL of 0.08 ug/L was exceeded in five Quaternary wells. However, median

concentrations were below the reporting limit of 0.01 ug/L. The 95th percentile and 95th

percent upper confidence limit concentrations exceeded the HRL for both the water-table



(QWTA) and buried unconfined (QBUA) aquifer groups, but not for the buried artesian

(QBAA) ground.

Beryllium concentrations were most strongly correlated with other trace metals

such as cadmium and silver, but were also negatively correlated with calcium, magnesium,

and silica. Beryllium is a divalent metal which can substitute for calcium, magnesium, and

silica in igneous rocks. Consequently, the areas in which beryllium concentrations are

greatest in Quaternary deposits occur where crystalline Precambrian and North Shore

Volcanic deposits are present. While most forms of beryllium have a low solubility, the

HRL is so low it will be exceeded in aquifers with parent material enriched in beryllium.

Beryllium is therefore a potential health concern.

Boron

There was just one exceedance of the HRL for boron (600 ug/L) in Quaternary

wells. The median concentrations were less than 50 ug/L in all three aquifer classes.

Boron was most strongly correlated with total dissolved solids and well depth, indicating

the role of residence time on boron concentrations. Concentrations of boron were

positively correlated with all major cations and anions. Boron does not appear to

represent a potential health concern in Quaternary aquifers of Region 1.

Iron

There were 47 exceedances of the Secondary Maximum Contaminant Limit

(SMCL) of 300 ug/L for iron. This represents about 57 percent of the sampled wells.

Median concentrations of iron exceeded the SMCL in all three Quaternary aquifer groups.

Iron was most strongly correlated with organic carbon and total suspended solids, but in

general, correlations between other chemicals and iron were weak. This contrasts with

results from other regions in the state, where iron was often correlated with the

distribution of several chemicals. Similarly, the correlation between iron and total

suspended solids was not as strong as for other regions of the state. The concentration of

iron in underlying bedrock aquifers is low and this may be responsible for the lack of



correlations between iron and other chemicals. The primary effect of iron is staining of

plumbing fixtures.

Manganese

There were four exceedances of the drinking criteria of 1000 ug/L used for

manganese. This value is an order of magnitude above the current HRL, which is

expected to be modified in the near future. The median concentration of manganese in the

drift aquifers was about 100 ug/L, with concentrations being greatest in the buried

unconfined aquifers (median = 157 ug/L). Either the 95th percentile or the upper 95th

percent confidence limit concentration exceeded the drinking water criteria for each of the

three aquifer groups.

The strongest correlation for manganese was with iron (0.40), but manganese was

also correlated with some trace elements such as arsenic and barium. The greatest

concentrations of manganese occurred in areas underlain by crystalline bedrock aquifers

(PCCR). These bedrock aquifers also had elevated concentrations of manganese but not

of arsenic and barium. The source of manganese in the Quaternary aquifers appears to be

underlying Precambrian bedrock. Manganese will be a potential health concern in about

five percent of wells completed in Quaternary aquifers, with the greatest potential risk

being in areas underlain by crystalline Precambrian bedrock.

Aluminum

Aluminum exceeded the SMCL of 50 ug/L in 13 Quaternary wells, which

represents about 15 percent of the sampled wells. The median concentration was less than

5.3 ug/L in all three Quaternary aquifer groups, but the 95th percentile and 95th percent

upper confidence limits were greater than 200 ug/L for the QWTA and QBAA groups.

The strongest correlations were with other trace metals such as chromium, cobalt, copper,

and lead (all positive), and with total suspended solids. Underlying Precambrian bedrock

was enriched in aluminum but there was no apparent correlation between high aluminum

concentrations in Precambrian bedrock aquifers and high concentrations in Quaternary

aquifers.



Lead

Lead exceeded the Action Level of 15 ug/L in one Quaternary well. The median

concentrations of lead in QBAA, QBUA, and QWTA wells were 0.21, 0.14, and 0.17

ug/L, respectively. Lead concentrations were most strongly correlated with other trace

metals such as cobalt, aluminum, chromium, and particularly copper. Concentrations

appeared to be greatest in areas underlain by Precambrian crystalline or North Shore

Volcanic aquifers. In general, however, lead does not represent a health concern in

QWTA wells of Region 1.

3.4.2. Precambrian aquifers

Precambrian deposits underlie the entire region. These units do not behave as

typical aquifers, however. Wells completed in bedrock units may actually intercept water

moving along the interface between drift and bedrock. There appears to be sufficient

residence time for this water to develop a water quality signature from the bedrock unit.

The different Precambrian units are therefore considered different aquifers in this report

because water quality differs between the different units. The objective of this discussion

is to identify potential water quality concerns and identify differences between the major

Precambrian aquifer groups.

The geology and mineralogy of a wide variety of Precambrian deposits are

described in the literature (Minnesota Geological Survey, 1970; Cotter et al., 1964;

Southwick, 1993; Sims, 1970; Minnesota Geological Survey, 1979; Minnesota Geological

Survey, 1982; Wright et al., 1970; Morey et al., 1970; Morey, 1967; Green, 1992; Jirsa et

al., 1991). It is beyond the scope of this paper to discuss these. Crystalline, North Shore

Volcanic, and undifferentiated Precambrian aquifers are discussed below.

3.4.2.1. Crystalline aquifers

Aquifers classified as crystalline (PCCR) encompass a wide range of bedrock but

consist primarily of metamorphosed igneous and sedimentary rocks. Water quality varies



with the formation in which a well is completed. The PCCR aquifers sampled during this

study cannot therefore be treated as a single aquifer system.

Comparison of GWMAP data with data from other literature sources is

summarized in Table A.25. Concentrations of most chemicals were relatively low in the

GWMAP data but were within the range reported in the literature. Concentrations of

fluoride and phosphorus were greater in the GWMAP data.

Ground water within the crystalline bedrock aquifers was, on average, oxygenated

and had a median Eh value of 266 mV. Concentrations of most chemical parameters were

low. Bicarbonate accounted for more than 90 percent of the total anion concentration,

while calcium and magnesium accounted for about 78 percent of the cation concentration.

There was large variability in concentrations of chemicals, with mean and median

concentrations differing by about 13 percent. This compares to 7.5 and 8.3 percent for

the water-table and North Shore Volcanic aquifer groups.

The importance of bicarbonate, calcium, and magnesium, and the presence of

oxygen reflect an impact from the unsaturated zone. This makes sense, since ground

water primarily occurs at the interface of the drift and bedrock. In addition to these

chemicals, there are elevated concentrations of arsenic, beryllium, manganese, selenium,

and fluoride, all of which may be related to mineralogy of the bedrock. The large

variability in water quality is reflected by comparing concentrations with drinking water

criteria. Concentrations of arsenic, beryllium, manganese, selenium, aluminum, fluoride,

iron, and sulfate exceeded drinking water criteria in at least one well from the PCCR

group. Each of these chemicals is discussed below.

Arsenic

The Maximum Contaminant Level (MCL) of 50 ug/L for arsenic was exceeded in

one well (157 ug/L). The median concentration of arsenic was 0.64 ug/L, but the 90th

percentile and upper 95th percent confidence limit concentrations were 49 and 28 ug/L.

There is general agreement that a health-based concentration for arsenic would be 10 ug/L

or lower. The observed concentrations of arsenic in crystalline bedrock aquifers thus

represent a potential health concern in at least five and probably more than 10 percent of



wells completed in these aquifers. Arsenic was negatively correlated with other trace

metals such as barium, vanadium, and zinc, and positively correlated with sodium and

boron. Arsenic is present in many wells at concentrations which are likely to represent

potential health concerns if a health-based drinking criteria is developed.

Beryllium

There were 3 exceedances of the HRL for beryllium (0.08 ug/L), although the

highest concentration was 0.51 ug/L. The median concentration of beryllium in sampled

PCCR wells was 0.020 ug/L. The strongest correlation for beryllium was with silica.

Beryllium can substitute for silica in minerals, thus supporting this correlation. The 90th

percentile and 95th percent upper confidence limit concentrations were both well above

the HRL (0.23 and 0.39 ug/L, respectively). Beryllium may represent a significant

potential health concern in Precambrian crystalline aquifers.

Manganese

The drinking criteria for manganese (1000 ug/L) was exceeded in one well (2087

ug/L). The current HRL for manganese is 100 ug/L and this value was exceeded in eight

wells. The 90th percentile concentration was 1191 ug/L, but the upper 95th percent

confidence limit concentration was only 399 ug/L. Manganese was not well correlated

with either the redox parameters (dissolved oxygen, Eh, iron) or with most trace elements.

The strongest correlations were with cobalt and selenium. The occurrence of elevated

manganese concentrations in ground water are difficult to understand with the existing

data, but if the HRL is amended to a concentration of 1000 ug/L or more, manganese will

not be a significant potential health concern in PCCR aquifers.

Selenium

The HRL for selenium (30 ug/L) was exceeded in one well (307.7). The next

highest concentration was 4.3 ug/L. The 90th percentile and 95th percent upper

confidence limit concentrations both exceeded the HRL (95 and 80 ug/L, respectively).



Selenium was correlated with manganese concentrations but not with most other

chemicals. Selenium is mobile in soil, but the lack of correlation with the redox

parameters suggest that dissolution of parent material may be a more important

mechanism for introducing selenium into ground water than leaching through the soil

zone. The single well in which selenium exceeded the HRL had a dissolved oxygen

concentration of 7340 ug/L, an Eh of 299 mV, and elevated concentrations of chromium

and beryllium. These suggest a potential leaching source in this well. In general, selenium

does not represent a potential health concern in wells completed in Precambrian crystalline

bedrock.

Aluminum

Aluminum exceeded the Secondary Maximum Contaminant Level of 50 ug/L in

five wells. The 90th percentile and 95th percent upper limit concentrations were 272 and

117 ug/L, respectively. Aluminum was well correlated with several trace metals, including

cobalt, chromium, lead, copper, and vanadium, but the strongest correlation was with total

suspended solids (0.80). The source of aluminum is dissolution of parent rock, but once

released from the bedrock, aluminum becomes associated with suspended material. This

material is most likely oxides and sesquioxides of iron, manganese, and other metals, since

aluminum was negatively correlated with organic matter concentrations. Aluminum can

have deleterious effects on aquatic life at low concentrations, but, despite the relatively

high concentrations, it does not appear to represent a significant concern for humans.

Fluoride

Fluoride exceeded the Maximum Contaminant Level of 4000 ug/L in one sample,

with the next highest concentration being 1450 ug/L. The median, 90th percentile, and

upper 95th percent confidence limit concentrations of fluoride were 490, 3258, and 1020

ug/L, respectively. Fluoride was not well coordinated with other chemical parameters,

with the greatest correlation being with sodium (R2 = 0.54). Fluoride has no specific

health effects but causes mottling of teeth. Concentrations of fluoride appear to be highly

variable in the PCCR aquifer, but in general do not appear to represent a concern.



Iron

The SMCL of 300 ug/L for iron was exceeded in six samples. The median

concentration of iron was 145 ug/L, which is low compared to most other aquifers in

Minnesota. There was considerable variability in the data, however, since the mean

concentration was 445 ug/L and the 90th percentile concentration was 20875 ug/L. Iron

was not well correlated with the redox parameters (Eh and dissolved oxygen), but was

significantly correlated with most trace elements. This may reflect the association of these

trace elements with iron as suspended materials. The primary effect of iron is on staining

of plumbing fixtures. Ground water with high concentrations of suspended material will

have iron concentrations exceeding the drinking water criteria. Filtering may be an option

for reducing iron content of ground water pumped from these aquifers.

Sulfate

Sulfate exceeded the SMCL of 250000 ug/L in one well, with the next highest

concentration being 55230 ug/L. The single well with the high sulfate concentration also

had very high concentrations of total dissolved and suspended solids, calcium, magnesium,

sodium, bicarbonate, arsenic, and aluminum. There was no apparent distribution to the

sulfate concentrations in sampled wells, but this may be due to the excessive concentration

in the one well. Sulfate does not represent a drinking water concern in Region 1.

3.4.2.2. North Shore Volcanics

The structure, stratigraphy, and geochemistry of the North Shore Volcanic Group

are discussed in Green, 1992. A limited discussion of the hydrology of aquifers occurring

within the North Shore Volcanic deposits is presented in Olcott et al. (1978). Aquifers

occur within fractures and may vary widely in age depending on individual flow paths

within the fractured bedrock. Despite this, the variability in concentrations of different

chemical parameters was not as great as for the other Precambrian groups. This may be



due to bedrock consisting primarily of olivine-rich material throughout the North Shore

Volcanic Group.

GWMAP data is compared to data from other literature sources in Table A.26.

Although the data available for comparison is limited, concentrations of bicarbonate and

iron were greater while chloride, sulfate, sodium, and total dissolved solid concentrations

were lower in the GWMAP data compared to the remainder of the data. The data from

Olcott et al. (1978) and from this study may be used to define a range of ground water

quality in the North Shore Volcanic Group.

Aquifers from the North Shore Volcanic group have low concentrations of

dissolved solids and occasional high concentrations of some trace metals, particularly

aluminum, boron, and beryllium. The high concentrations of aluminum and iron reflect

dissolution of parent material, which is rich in iron and aluminum. Sodium accounts for a

relatively high percentage of the concentration of total cations, but sodium concentrations

are well below drinking water criteria. The water quality comparisons indicate parent

material has a much larger effect on water quality of the North Shore Volcanic group than

for other Precambrian aquifers. This may be due to increased importance of fractures in

ground water hydrology compared to other aquifers. There were exceedances of drinking

water criteria for aluminum, beryllium, boron, iron, and lead in at least one well sampled

from the North Shore Volcanic Group. These chemicals are discussed below.

Aluminum

Aluminum exceeded the Secondary Maximum Contaminant Level (SMCL) of 50

ug/L in six samples. The overall mean and median concentrations of aluminum in the

PMNS aquifer group were 45 and 49 ug/L, meaning nearly 50 percent of wells completed

in this formation exceed the drinking criteria. Aluminum concentrations were strongly

correlated with concentrations of other trace metals, including copper, chromium, cobalt,

zinc, and antimony. Aluminum was also strongly correlated with concentrations of total

suspended solids. Since aluminum was negatively correlated with organic carbon, it

appears to be associated with other metal complexes in ground water. Filtering may thus

be an option for removing some aluminum from ground water.



Aluminum is toxic to aquatic life at low concentrations. Because aquifers occur

within fractures, rapid transport systems may pose potential risk to ecological receptors.

Information on aluminum concentrations from surface waters is limited for the North

Shore Region of Lake Superior, where North Shore Volcanic deposits occur. However,

ground water is likely to be a small contributor to the water budget of most lakes and

streams because of the low permeability of surficial deposits.

Beryllium

The HRL for beryllium (0.08 ug/L) was exceeded in two samples. The overall

mean and median concentrations were 0.018 and 0.025 ug/L. The 90th percentile and

95th percent upper confidence limit concentrations were 1.8 and 2.1 ug/L, respectively,

which exceed the HRL. Beryllium was strongly correlated with other metals such as zinc,

iron, lead, antimony, and copper. It was also positively correlated with dissolved oxygen,

despite the strong positive correlation with iron. These conflicting results indicate

dissolution of parent material is the dominant process affecting the concentration of

beryllium in ground water, but redox reactions may also be important in some aquifers.

Beryllium is a potential drinking water concern in wells completed within the North Shore

Volcanic Group.

Boron

The HRL for boron (600 ug/L) was exceeded in 2 wells. The overall mean and

median concentrations were 182 and 219 ug/L. The 90th percentile and 95th percent

upper limit concentrations of 1795 and 3980 ug/L, respectively, are above the HRL.

Boron was positively correlated with trace metals such as aluminum, cobalt, and copper,

but was most strongly correlated with chloride, sulfate, sodium, selenium, and total

dissolved solids. These results reflect the higher solubility of boron compared to most

trace metals. Boron represents a potential health risk in wells completed in deposits from

the North Shore Volcanic Group.

Iron



Iron exceeded the SMCL (300 ug/L) in 5 samples. Mean and median

concentrations were 266 and 204 ug/L, respectively. The upper 95th percent confidence

limit concentration was 1100 ug/L. Iron was strongly correlated with other trace metals

such as lead, copper, chromium, and antimony. Iron was also well correlated with silicate,

reflecting the dissolution of parent material (olivine-rich bedrock). Iron was correlated

with total suspended solid concentrations but not with organic carbon concentrations.

Filtering may reduce concentrations of iron in ground water. The primary concern with

high iron concentrations is staining of plumbing fixtures.

Lead

The Action Level for lead of 15 ug/L was exceeded in one well (16.08 ug/L). The

next highest concentrations of lead were 6.38 and 1.26 ug/L. The 95th percent upper limit

concentration was 1.4 ug/L. Lead was most strongly correlated with other trace metals

such as beryllium, chromium, copper, and aluminum. As with the other trace metals, lead

was strongly associated with concentrations of suspended solids. The well with the single

exceedance of the drinking water criteria also had a suspended solid concentration of

192000 ug/L, well above the median concentration of 4500 ug/L. Lead does not appear

to represent a drinking water concern in Region 1.

3.4.2.3. Undifferentiated Precambrian Aquifers

Because of the complex nature of bedrock deposits in Region 1, the type of

geologic material comprising many aquifers cannot be identified clearly from well logs.

These include a wide variety of metamorphosed igneous and sedimentary rocks. If all

undifferentiated aquifers are combined into a single group, the mineralogy of this group

will be highly variable. Consequently, the overall average difference in mean and median

concentration for sampled chemical parameters from the undifferentiated group (PMUD)

was greater than 20 percent.

Aquifers occur both along the drift-bedrock interface and within bedrock fractures.

Ground water may thus be part of a rapid response system with high conductivity, or may

become entrapped in dead-end fractures and therefore have a very long residence time.



The concentrations of chemical parameters reported in other studies are comparable to the

concentrations found in this study (Table A.24). Water quality is, in general, good,

although concentrations of iron are high. Water is primarily of the calcium-magnesium-

bicarbonate type, but concentrations of dissolved solids are relatively low and sodium may

account for a significant portion of the total concentration of cations in some wells.

Exceedances of drinking water criteria were found for beryllium, boron,

manganese, selenium, aluminum, chloride, and iron in at least one sampled well. These

chemicals are discussed below.

Beryllium

The HRL of 0.08 ug/L for beryllium was exceeded in one well. Overall mean and

median concentrations were 0.0059 and 0.0075 ug/L, respectively. The 95th percentile

(0.35) and upper 95th percent confidence limit (0.17) concentrations exceeded the

drinking criteria.

The strongest correlations were with aluminum, chromium, iron, lead, and total suspended

solids. Beryllium appears to represent a slight potential health concern in these aquifers.

Boron

The HRL of 600 ug/L for boron was exceeded in one well (635.4 ug/L) and there

were four additional wells in which the concentration exceeded 100 ug/L. However, the

mean and median concentrations were 45 and 37 ug/L, well below the drinking criteria.

Both the upper 95th percentile (626 ug/L) and upper 95th percent confidence limit (662

ug/L) concentrations were slightly greater than the HRL. The only significant

correlations were with pH and sodium. Boron does not represent a significant potential

health risk in PMUD aquifers in Region 1, although about 5 percent of sampled wells will

exceed the drinking water criteria.

Manganese

The drinking criteria for manganese (1000 ug/L) was exceeded in one well (2507.5

ug/L). The next highest concentration was 621.5 ug/L. Mean and median concentrations



were 45 and 70 ug/L, and the upper 95th percent confidence limit concentration of 123

ug/L is well below the drinking criteria. Manganese does not represent a potential health

concern in Region 1.

Selenium

The HRL for selenium (30 ug/L) was exceeded in one well (92.5 ug/L). The mean

and median concentrations were both 2.0 ug/L. The 95th percentile and upper 95th

percent confidence limit concentrations were 89 and 36 ug/L, respectively. Selenium was

not well correlated with any chemical parameter. There was a positive correlation with Eh

which may reflect the tendency for higher selenium concentrations in oxygenated ground

water, but it is unclear if the source of the selenium is the soil or aquifer material.

Selenium represents a potential health concern in just over 5 percent of wells completed in

the PMUD aquifer.

Aluminum

Aluminum exceeded the Secondary Maximum Contaminant Level of 50 ug/L in

two wells. The mean and median concentrations were 4.2 and 6.5 ug/L, while the upper

95th percent confidence limit concentration was 197 ug/L. The greatest correlations were

with beryllium, iron, chromium, lead, vanadium, and suspended solids. As with other

Precambrian aquifers, aluminum concentrations in ground water are a function of parent

material, and aluminum primarily forms complexes with other metals in ground water.

Chloride

The SMCL of 250000 ug/L for chloride was exceeded in one well. This well had a

concentration of 5029000 ug/L, or about 0.5%. There were no other chemical

concentrations which exceeded a drinking criteria in this well. The sample appears to have

been contaminated, either by recent chlorination of the well or by addition of hydrochloric

acid to the sample bottle. The median concentration of 2275 ug/L is well below the

SMCL. Chloride does not represent a drinking water concern in Region 1.



Iron

The SMCL for iron (300 ug/L) was exceeded in 10 of the 20 wells sampled. The

mean and median concentrations were 297 and 298 ug/L. The upper 95th percent

confidence limit concentration was 680 ug/L. As with other Precambrian aquifers, iron

concentrations were most strongly correlated with other trace metals and suspended

solids. Because of the association with suspended solids, it is difficult to determine if iron

represents a concern in ground water, but concentrations of iron are high compared to

most other aquifers of Region 1.

3.5. Volatile Organic Compounds (VOCs)

VOC results are summarized in Table A.27. The distribution of VOC samples and

detections are illustrated in Figure B.7. There were 28 wells in which a VOC was

detected. This represents 20 percent of the sampled wells, which is greater than the

overall statewide rate of 11 percent. There were two wells in which more than one VOC

was detected. Eleven of the 30 total detections were chloroform. Chloroform may

represent a by-product of well disinfection, but chloroform and other trihalomethane

compounds may also be naturally occurring. Nine of the detections were compounds

which may be associated with fuel oil leaks or spills, although all but one of these was

toluene and the concentrations were less than 0.5 ug/L. Eight of the detections were

fluorocarbon compounds, which accounts for 27 percent of the VOC detections. This was

well above the statewide rate of 7 percent. Fluorocarbons may be the result of

atmospheric fallout. Only one compound was a chlorinated solvent, which are generally

associated with industrial uses.

Eight of the VOC detections were in the QBAA aquifer group, seven were in the

PCCR aquifer group, and there were three each in the PMNS, PMUD, QBUA, and

QWTA groups. The occurrence of VOCs was not associated with any chemical. Median

concentrations of dissolved oxygen were below the detection limit for samples with and

without detectable VOCs, and the Eh of these two groups were equal. The frequency of

detecting tritium in samples with a detected VOC was 83 percent, while the frequency was



71 percent in wells with no detectable VOC. There was no significant difference in well

depth or static water elevation in samples with and without a detectable VOC. The

occurrence of VOCs in ground water appears to be somewhat random, being dependent

on a source for the VOC.

There were no exceedances of drinking criteria. Overall, VOCs do not represent a

drinking water concern in Region 1.

4. Summary and Recommendations

This chapter is divided into a section providing a summary of the results, a section

providing recommendations for additional research, and a section providing monitoring

recommendations.

4.1. Summary

1. Summary statistics (median, minimum, maximum, mean, 95th confidence limit, and

90th or 95th percentile concentrations) for a wide range of chemical parameters have

been calculated for 12 aquifer groups sampled in MPCA Region 1 in northeast

Minnesota. Sample size was sufficient for the Precambrian crystalline (PCCR), North

Shore Volcanic (PMNS), undifferentiated Precambrian (PMUD), buried artesian drift

(QBAA), buried unconfined drift (QBUA), and surficial drift (QWTA) aquifer groups

for these values to serve as background concentrations for the aquifers in Region 1.

2. There were differences in concentrations of many chemicals between different aquifer

groups. Buried and surficial drift aquifers had very similar water quality, including

higher concentrations of arsenic, iron, phosphorus, and silicate, and lower

concentrations of aluminum, beryllium, lead, sodium, and zinc compared to the

Precambrian aquifers. The Precambrian aquifers had a wide variability in

concentrations of chemicals. Concentrations of boron, beryllium, fluoride, and sodium

were greatest in the PMNS aquifer group, while arsenic concentrations were greatest

in the PMUD group. Concentrations of many chemicals were lower in the PMNS

group compared to other Precambrian groups, including alkalinity, potassium, organic



carbon, magnesium, barium, calcium, and manganese. Water quality of aquifers was

most affected by parent material, particularly for the Precambrian aquifers.

3. Ground water quality of Precambrian aquifers reflects impacts from both the

unsaturated zone and bedrock units. Ground water in Precambrian aquifers is of the

calcium-magnesium-bicarbonate type, similar to that of the buried drift aquifers.

Concentrations of many trace chemicals, such as boron, beryllium, and copper, are

greater in Precambrian aquifers, reflecting mineralogy of the different bedrock units.

4. Health-based drinking standards (HRL or HBV) were exceeded for the following

compounds:

• manganese - 6 exceedances, primarily in drift aquifers;

• boron - 5 exceedances, primarily in Precambrian aquifers;

• beryllium - 12 exceedances in Precambrian and drift aquifers;

• selenium - 1 exceedance in a PCCR aquifer; and

• arsenic - 1 exceedance in a PCCR aquifer.

5. Non-health based standards (MCL or SMCL) were exceeded for the following

compounds:

• iron - 70 exceedances, scattered among all aquifers;

• aluminum - 28 exceedances in Precambrian and drift aquifers;

• sulfate - 1 exceedance in a PCCR aquifer;

• chloride - 1 exceedance in a PMUD aquifer;

• lead - 4 exceedances of the action level of 15 ug/L, primarily in Precambrian

aquifers; and

• fluoride - 1 exceedance in a PCCR aquifer.

6. Median concentrations of many chemicals in all aquifers of Region 1 varied in

comparison with statewide median concentrations for similar aquifers. Median

concentrations of chemicals which reflect leaching, such as bicarbonate, selenium,

antimony, vanadium, calcium, and nitrate, were lower in Region 1 aquifers compared

to similar aquifers statewide. Concentrations of trace elements were higher. The

primary trace elements of concern include beryllium, boron, aluminum, and lead.

Beryllium and boron have health-based drinking water criteria, while the drinking



criteria for iron and aluminum is not health-based. Iron and aluminum concentrations

exceeded or were near the drinking criteria in a high percentage of wells in all aquifers,

while the high rates of exceedance for boron and beryllium were primarily in the

Precambrian aquifers. The primary control on concentrations of boron, aluminum,

iron, and beryllium appears to be parent material.

7. Volatile organic compounds were detected in 28 wells or 20 percent of the samples.

Trihalomethane compounds, primarily chloroform, were the most common VOC

found. Fuel oil compounds were detected next most frequently. No drinking water

criteria for VOCs was exceeded.

4.2. Research Recommendations

The objective of research is to provide information relating physical processes to

water quality. Although research is typically conducted at small scales, results should

have widespread application. GWMAP conducts research related to impacts of human

activity on ground water quality. Research recommendations for Region 1 are discussed

below.

1. A better understanding of ground water hydrology is required before water quality can

be related to hydrologic processes. In particular, the following questions should be

addressed:

• What are residence times of ground water accumulating and moving along the

bedrock-drift interface?

• How important are fracture systems in ground water hydrology?

• What are the mechanisms of chemical dissolution of bedrock and how do these

relate to potential health impacts for drinking water receptors?

2. Land use information needs to be collected to determine if there is a relationship

between the high frequency of VOC detection and human activity.

3. Bedrock aquifers need to be classified so that water quality can be related to

hydrologic and geochemical conditions. In particular, individual well logs should be

examined when considering water quality, since wells classified as being completed in

Precambrian aquifers may be completed across the bedrock-drift interface.



4.3. Monitoring Needs

The objective of ground water monitoring is to provide information which can

serve as a point of reference for ground water quality. Baseline monitoring is used to

provide data which can be compared with site-specific or regional data. Ambient

monitoring includes a time component and is intended to provide information regarding

long-term trends in water quality of an aquifer. Monitoring needs for Region 1 are

discussed below.

1. Baseline data : the baseline data for the buried confined drift (QBAA), and surficial

drift (QWTA) aquifers is sufficient to be considered representative of background.

These data can simply be updated over time. Data bases for the Precambrian aquifers

should be expanded and the data reanalyzed to establish baseline conditions.

Information in this report provides an initial estimate of background water quality in

these aquifers, but the values may change as additional data is incorporated. The

following specific recommendations are made for baseline enhancement.

• Expand the database for PCCR, PMNS, and PMUD aquifers by about 20 wells

each. Wells selected for sampling should have well logs and would preferably

be grouted. The wells do not need to be located within GWMAP grid cells.

The parameter list includes major cations and anions and the inorganic trace

elements. In addition to using the 4-letter CWI code, additional effort should

be made to determine specific formations the PCCR and PMUD aquifers are

completed in. This may reduce some of the variability in the water quality data

for these two aquifers.

• Sample for VOCs in approximately 50 additional wells across Region 1.

Sampling would primarily be done in Precambrian aquifers, particularly

aquifers classified as PCCR. The data would be used to verify the distribution

of VOCs found in the current study. When developing an ambient network for

VOC analysis, it is important to verify where wells are completed in the

geologic formations.



• Analysis of the data should be conducted at approximately five to ten year

intervals, provided data have been collected during this period. Analysis

methods similar to those employed by GWMAP should be used.

• Data from other studies can be incorporated into the baseline data base. Field

sampling methods must be documented and meet standard QA/QC protocol.

2. Ambient monitoring : ambient monitoring is needed in aquifers impacted by humans.

At this time, VOCs are the only potential chemical of concern related to human

activity in Region 1, particularly in Precambrian aquifers. It is unclear, however, if the

high incidence of VOC detections is related to human activity and what the potential

health implications of VOCs are. An ambient network should not be established,

therefore, until the link between human activity and incidence of VOC detections has

been proven.

3. Sampling, data management, and data analysis protocol should be established and

documented. Protocol developed by other agencies or ground water groups can be

utilized.



References

Cotter, R.D., H.L. Young, and T.C. Winter. 1964. Preliminary Surficial Geologic Map

of the Mesabi-Vermilion Iron Range Area, Northeastern Minnesota. Misc. Map

Series I-403. United States Geological Survey. 1 plate.

Ericson, D.W., G.F. Lindholm, and J.O. Helgeson. 1976. Water Resources of the Rainy

Lake Watershed, Northeastern Minnesota. Hydrologic Investigations Atlas HA-556.

United States Geological Survey. 2 plates.

Green, J.C. 1992. Geologic Map of the North Shore of Lake Superior, Lake and Cook

Counties, Minnesota: Part 1. Little Marais to Tofte. Misc. Map Series M-71.

University of Minnesota. St. Paul, MN. 1 plate.

Helgeson, J.O., G.F. Lindholm, and D.W. Ericson. 1976. Water Resources of the Little

Fork River Watershed, Northeastern Minnesota. Hydrologic Investigations Atlas HA-

551. United States Geological Survey. 2 plates.

Jirsa, M.A., T.J. Boerboom, V.W. Chandler, and P.L. McSwiggen. 1991. Bedrock

Geologic Map of the Cook to Side Lake Area, St. Louis and Itasca Counties,

Minnesota. Misc. Map Series. Map M-75. University of Minnesota. St. Paul, MN. 1

plate.

Lindholm, G.F., D.W. Ericson, W.L. Broussard, and M.F. Hult. 1979. Water Resources

of the St. Louis River Watershed, Northeastern Minnesota. Hydrologic Investigations

Atlas HA-586. United States Geological Survey. 3 plates.

Lindholm, G.F., J.O. Helgeson, and D.W. Ericson. 1974. Water Resources of the Big

Fork River Watershed, North-Central Minnesota. Hydrologic Investigations Atlas

HA-549. United States Geological Survey. 2 plates.



Minnesota Department of Health. 1997. Health Based Value for Manganese. Office

Memorandum by Larry Gust, Supervisor, Health Risk Assessment Unit. St. Paul, MN.

1 p.

Minnesota Geological Survey. 1982. Geologic Map of Minnesota - Two Harbors Sheet.


Minnesota Geological Survey. 1979. Geologic Map of Minnesota - International Falls

Sheet. University of Minnesota. St. Paul, MN. 1 plate.

Minnesota Geological Survey. 1970. Geologic Map of Minnesota - Hibbing Sheet.


Minnesota Pollution Control Agency. 1994. Ground Water Monitoring and Assessment

Program (GWMAP) Annual Report. St. Paul, MN. 182 p.

Minnesota Pollution Control Agency. 1995. Ground Water Monitoring and Assessment

Program (GWMAP) Annual Report. St. Paul, MN. 116 p.

Minnesota Pollution Control Agency. 1996. GWMAP Field Guidance Manual. St. Paul,

MN. 42p.

Minnesota Pollution Control Agency. 1998a. Baseline Water Quality of Minnesota’s

Principal Aquifers. St. Paul, MN. 145p. and appendices.

Minnesota Pollution Control Agency. 1998b. Data Analysis Protocol for the Ground

Water Monitoring and Assessment Program (GWMAP). Draft in review.



Morey, G.B. 1967. Stratigraphy and Petrology of the Type Fond du Lac Formation,

Dultuth, Minnesota. Report of Investigations 7. University of Minnesota.

Minneapolis, MN. 35 pp.

Morey, G.B., J.C. Green, R.W. Ojakangas, and P.K. Sims. 1970. Stratigraphy of the

Lower Precambrian Rocks in the Vermilion District, Northeastern Minnesota. Report

of Investigations 14. University of Minnesota. Minneapolis, MN. 33 pp.

Myers, Georgianna, S. Magdalene, D. Jakes, E. Porcher. 1992. The Redesign of the

Ambient Ground Water Monitoring Program. Minnesota Pollution Control Agency.

St. Paul, MN. 151 p.

Olcott, P.G., D.W. Ericson, P.E. Felsheim, and W.L. Broussard. 1978. Water Resources

of the Lake Superior Watershed, Northeastern Minnesota. Hydrologic Investigations

Atlas HA-582. United States Geological Survey. 2 plates.

Sims, P.K. 1970. Geologic Map of Minnesota. Misc. Map Series M-14. Minnesota

Geological Survey - University of Minnesota. Minneapolis, MN. 1 plate.

Southwick, D.L. 1993. Geologic Map of Archean Bedrock, Soudan-Bigfork Area,

Northern Minnesota. Misc. Map Series M-79. University of Minnesota. St. Paul,

MN. 1 plate.

Wahl, T. E., and R. G. Tipping. 1991. Ground-water Data Management - The County

Well Index. Minnesota Geological Survey. Minneapolis, MN. 38 p.

Wright, H.E. Jr., L.A. Mattson, and J.A. Thomas. 1970. Geology of the Cloquet

Quadrangle. Geologic Map Series GM-3. University of Minnesota-Minnesota

Geological Survey. Minneapolis, MN. 30 pp. and 1 plate.



Appendix A - Tables

1. Distribution of samples, by aquifer.2. Summary information for all chemical parameters. Censoring values were established

just below the maximum reporting limit.3. Descriptive statistics for the Mount Simon-Hinckley Formation (CMSH).4. Descriptive statistics for undifferentiated Precambrian formations (PCCR).5. Descriptive statistics for undifferentiated Precambrian crystalline formations (PCUU).6. Descriptive statistics for the Biwabik Iron Formation (PEBI).7. Descriptive statistics for the Duluth Complex (PMDC).8. Descriptive statistics for the Mount Simon-Fond du Lac Formation (PMFL).9. Descriptive statistics for the Hinckley Formation (PMHN).10. Descriptive statistics for the North Shore Volcanics Group (PMNS).11. Descriptive statistics for undifferentiated Proterozoic Metasedimentary units (PMUD).12. Descriptive statistics for buried Quaternary artesian aquifers (QBAA).13. Descriptive statistics for unconfined buried Quaternary aquifers (QBUA).14. Descriptive statistics for Quaternary water table aquifers (QWTA).15. Coefficients for log-censored data from analysis of descriptive statistics, for each

aquifer and chemical. See MPCA, 1998a, for application of these coefficients.16. Coefficients for log-normal data from analysis of descriptive statistics, for each aquifer

and chemical. See MPCA, 1998a, for application of these coefficients.17. Median concentrations, in ug/L, of sampled chemicals for each of the major aquifers.

The p-value indicates the probability that aquifers have equal concentrations.18. Median concentrations of chemicals in buried Quaternary and Precambrian bedrock

aquifers. An asterisk indicates chemicals for which concentrations differed betweenthe two aquifer groups. Concentrations are in ug/L except for pH, temperature (oF),specific conductance (umhos/cm), and Eh (mV).

19. Summary of water quality criteria, basis of criteria, and endpoints, by chemicalparameter.

20. Number of samples exceeding health-based water quality criteria, by aquifer.21. Percentage of samples exceeding health-based water quality criteria, by aquifer.22. Number of samples exceeding non-health-based water quality criteria, by aquifer.23. Percentage of samples exceeding non-health-based water quality criteria, by aquifer.24. Comparison of water quality data for Quaternary glacial drift aquifers from different

literature sources for Northeast Minnesota. Concentrations represent median values,in ug/L (ppb)1.

25. Comparison of water quality data for Precambrian bedrock aquifers from differentliterature sources for Northeastern Minnesota. Concentrations represent medianvalues, in ug/L (ppb)1.

26. Comparison of water quality data for North Shore Volcanic aquifers from differentliterature sources for Northeast Minnesota. Concentrations represent median values,in ug/L (ppb)1.

27. Summary of VOC detections for Region 1.Table A.1 : Distribution of samples, by aquifer.



Aquifer Number of SamplesMount Simon-Hinckley (CMSH) 1Precambrian Crystalline (PCCR) 16Precambrian undifferentiated (PCUU) 1Biwabik Iron Formation (PEBI) 1Duluth Complex (PMDC) 1Fond du Lac Formation (PMFL) 1Hinckley (PMHN) 1North Shore Volcanics (PMNS) 12Precambrian undifferentiated (PMUD) 20Quaternary buried artesian aquifer (QBAA) 52Quaternary buried unconfined aquifer (QBUA) 12Quaternary water table aquifer (QWTA) 21

Table A.2 : Summary information for all chemical parameters. Censoring valueswere established just below the maximum reporting limit.

Chemical Number ofsamples

Number ofmissing

Maximumreporting limit

(ug/L)

Number ofdetections abovecensoring value

Numbercensored

valuesAlkalinity 137 2 nnd1 137 0Aluminum 139 0 0.060 132 7Antimony 139 0 0.0080 79 60Arsenic 139 0 0.060 124 15Barium 139 0 1.4 134 5Beryllium 139 0 0.010 75 64Bismuth 76 63 0.040 1 75Boron 139 0 13 120 19Bromide 139 0 0.20 1 138Cadmium 139 0 0.020 56 83Calcium 139 0 nnd 139 0Cesium 76 63 0.010 40 36Chloride 139 0 200 139 0Chromium 139 0 0.050 132 31Cobalt 139 0 0.0020 138 1Copper 139 0 5.5 70 69Dissolvedoxygen

139 0 nnd 32 107

Table A.2 continued.

Maximum Number of Number




Numbermissing

reporting limit(ug/L)

detections abovecensoring value

censoredvalues

Eh 139 0 nnd 139 0Fluoride 109 30 2 109 0Iron 139 0 3.2 138 1Lead 139 0 0.030 130 9Lithium 139 0 4.5 79 60Magnesium 139 0 nnd 139 0Manganese 139 0 0.90 136 3Molybdenum 139 0 4.2 41 98Nickel 139 0 6.0 41 98Nitrate-N 139 0 500 14 125pH 137 2 nnd 137 0Phosphorus 139 0 14.9 113 26Potassium 139 0 118.5 136 3Rubidium 139 0 555.3 8 130Selenium 139 0 1.0 95 44Silicate 139 0 nnd 139 0Silver 139 0 0.0090 64 75Sodium 139 0 nnd 139 0SpecificConductance

137 2 nnd 137 0

Strontium 139 0 nnd 139 0Sulfate 139 0 300 125 14Sulfur 139 0 21.8 138 1Temperature 137 2 nnd 137 0Thallium 139 0 0.0050 38 101Tin 76 63 0.040 54 22Titanium 139 0 0.0035 40 90Total dissolvedsolids

139 0 nnd 139 0

Total organiccarbon

139 0 500 134 5

Total suspendedsolids

139 0 nnd 139 0

Vanadium 139 0 4.7 66 73Zinc 139 0 2.7 126 13Zirconium 76 63 0.030 54 22



Table A.2 continued


Numbermissing

Maximumreporting

limit (ug/L)


Numbercensored

values1,1-Dichloroethane 139 - 0.2 - -1,1-Dichloroethene 139 - 0.5 - -1,1-Dichloropropene 139 - 0.2 - -1,1,1-Trichloroethane 139 - 0.2 - -1,1,1,2-Tetrachloroethane 139 - 0.2 - -1,1,2-Trichloroethane 139 - 0.2 - -1,1,2,2-Tetrachloroethane 139 - 0.2 - -1,1,2-Trichlorotrifluoroethane

139 - 0.2 - -

1,2-Dichlorobenzene 139 - 0.2 - -1,2-Dichloroethane 139 - 0.2 - -1,2-Dichloropropane 139 - 0.2 - -1,2,3-Trichlorobenzene 139 - 0.5 - -1,2,3-Trichloropropane 139 - 0.5 - -1,2,4-Trichlorobenzene 139 - 0.5 - -1,2,4-Trimethylbenzene 139 - 0.5 - -1,3-Dichlorobenzene 139 - 0.2 - -1,3-Dichloropropane 139 - 0.2 - -1,3,5-Trimethylbenzene 139 - 0.5 - -1,4-Dichlorobenzene 139 - 0.2 - -2,2-Dichloropropane 139 - 0.5 - -2-Chlorotoluene 139 - 0.5 - -4-Chlorotoluene 139 - 0.5 - -Acetone 139 - 20 - -Allyl chloride 139 - 0.5 - -Bromochloromethane 139 - 0.5 - -Bromodichloromethane 139 - 0.2 - -Benzene 139 - 0.2 - -Bromobenzene 139 - 0.2 - -Bromoform 139 - 0.5 - -Bromomethane 139 - 0.5 - -cis-1,2-Dichloroethene 139 - 0.2 - -cis-1,3-Dichloropropene 139 - 0.2 - -Carbon tetrachloride 139 - 0.2 - -Chlorodibromomethane 139 - 0.5 - -Chlorobenzene 139 - 0.2 - -Chloroethane 139 - 0.5 - -Chloroform 139 - 0.1 - -





Number ofmissing

Maximumreporting

limit (ug/L)


Number ofcensored

valuesChloromethane 139 - 0.5 - -1,2-Dibromo-3-chloropropane

139 - 0.5 - -

Dibromomethane 139 - 0.5 - -Dichlorodifluoromethane 139 - 0.5 - -Dichlorofluoromethane 139 - 0.5 - -1,2-Dibromoethane 139 - 0.5 - -Ethylbenzene 139 - 0.2 - -Ethyl ether 139 - 2 - -Hexachlorobutadiene 139 - 0.5 - -Isopropylbenzene 139 - 0.5 - -Methylene chloride 139 - 0.5 - -Methyl ethyl ketone 139 - 10 - -Methyl isobutyl ketone 139 - 5 - -Methyl tertiary butyl ether 139 - 2 - -n-Butylbenzene 139 - 0.5 - -Naphthalene 139 - 0.5 - -n-Propylbenzene 139 - 0.5 - -o-Xylene 139 - 0.2 - -p&m-Xylene 139 - 0.2 - -p-Isopropyltoluene 139 - 0.5 - -sec-Butylbenzene 139 - 0.5 - -Styrene 139 - 0.5 - -tert-Butylbenzene 139 - 0.5 - -trans-1,2-Dichloroethene 139 - 0.1 - -trans-1,3-Dichloropropene 139 - 0.2 - -Trichloroethene 139 - 0.1 - -Trichlorofluoromethane 139 - 0.5 - -Tetrachloroethene 139 - 0.2 - -Tetrahydrofuran 139 - 10 - -Toluene 139 - 0.2 - -Vinyl chloride 139 - 0.5 - -1 nnd = no samples were below the maximum reporting limit2 Fluoride was censored at several detection limits. Censoring at the highest detectionlimit would result in only a few values above the censoring limit. Consequently, all non-detections were treated as missing data and removed from the data set.



Table A.3 : Descriptive statistics for the Mount Simon-Hinckley Formation(CMSH).

Chemical No. ofsamples

No. valuescensored

Distribution Mean UCLmean

Median 95thpercentile

Min Max StateMedian

ug/L ug/L

Alkalinity 1 0 ins ins ins 139000 ins - - 132500

Aluminum 1 0 ins ins ins < 0.060 ins - - 1.2

Antimony 1 0 ins ins ins 0.010 ins - - 0.010

Arsenic 1 0 ins ins ins 1.2 ins - - 0.86

Barium 1 0 ins ins ins 80 ins - - 57

Beryllium 1 0 ins ins ins 0.010 ins - - < 0.010

Boron 1 0 ins ins ins 300 ins - - 23

Bromide 1 1 ins ins ins < 0.20 ins - - < 0.20

Cadmium 1 0 ins ins ins 0.080 ins - - < 0.020

Calcium 1 0 ins ins ins 16692 ins - - 43648

Chloride 1 0 ins ins ins 36070 ins - - 2135

Chromium 1 0 ins ins ins 0.55 ins - - 0.25

Cobalt 1 0 ins ins ins 0.11 ins - - 0.41

Copper 1 1 ins ins ins < 5.5 ins - - 5.7

Dissolvedoxygen

1 1 ins ins ins < 300 ins - - 630

Eh 1 0 ins ins ins 75 ins - - 212

Fluoride 1 0 ins ins ins 580 ins - - 225

Iron 1 0 ins ins ins 164 ins - - 387

Lead 1 0 ins ins ins 0.070 ins - - 0.17

Lithium 1 0 ins ins ins 6.0 ins - - 7.0

Magnesium 1 0 ins ins ins 5591 ins - - 13269

Manganese 1 0 ins ins ins 28 ins - - 44

Molybdenum 1 1 ins ins ins < 4.2 ins - - < 4.2

Nickel 1 1 ins ins ins < 6.0 ins - - < 6.0

Nitrate-N 1 1 ins ins ins < 500 ins - - < 500

pH 1 0 ins ins ins 8.1 ins - - 7.3

Phosphorus 1 0 ins ins ins 33 ins - - 34

Potassium 1 0 ins ins ins 2478 ins - - 1292

Redox 1 0 ins ins ins -145 ins - - -3.0

Rubidium 1 1 ins ins ins < 555 ins - - < 555

Selenium 1 1 ins ins ins < 1.0 ins - - 1.6

Silicate 1 0 ins ins ins 4313 ins - - 10894

Silver 1 0 ins ins ins 0.020 ins - - < 0.0090

Sodium 1 0 ins ins ins 66103 ins - - 3823

SpecificConductance

1 0 ins ins ins 87 ins - - 304

Strontium 1 0 ins ins ins 189 ins - - 109

Sulfate 1 0 ins ins ins 17040 ins - - 1735

Sulfur 1 0 ins ins ins 6050 ins - - 1948

Temperature 1 0 ins ins ins 8.9 ins - - 8.7

Thallium 1 0 ins ins ins 0.010 ins - - < 0.0050

Titanium 1 1 ins ins ins < 0.0035 ins - - < 0.0035

Total dissolvedsolids

1 0 ins ins ins 238000 ins - - 218000





No. valuescensored



Min Max StateMedian

Total organiccarbon

1 0 ins ins ins 1500 ins - - 1850

Totalphosphate-P

1 1 ins ins ins < 20 ins - - 20

Totalsuspended

solids

1 0 ins ins ins 2000 ins - - 5000

Vanadium 1 1 ins ins ins < 4.7 ins - - 4.9

Zinc 1 1 ins ins ins < 2.7 ins - - 12

Table A.4 : Descriptive statistics for undifferentiated Precambrian formations(PCCR).


No. valuescensored



Min Max StateMedian

ug/L ug/L ug/L ug/L ug/L ug/L ug/LAlkalinity 16 0 log-normal 188018 270334 135500 443000 54000 541000 211000

Aluminum 16 0 log-normal 16 45 13 272 1.4 467 9.4

Antimony 16 5 log-censored 0.017 0.13 0.018 0.062 < 0.0080 0.090 0.014

Arsenic 16 3 log-censored 0.70 28 0.64 49 < 0.060 157 0.64

Barium 16 0 log-normal 43 69 38 139 10 173 39

Beryllium 16 6 log-censored 0.019 0.39 0.020 0.23 < 0.010 0.51 0.020

Boron 16 1 log-censored 49 603 49 395 < 13 592 55

Bromide 16 16 ins ins ins < 0.20 ins < 0.20 0.10 < 0.20

Cadmium 16 8 log-censored 0.026 0.81 0.020 0.35 < 0.020 0.47 0.020

Calcium 16 0 log-normal 46505 77144 31747 190363 11585 309399 38909

Chloride 16 0 log-normal 3506 7997 3220 22999 360 28830 2680

Chromium 16 4 log-censored 0.45 4.1 0.49 2.8 < 0.050 4.3 0.61

Cobalt 16 0 normal 0.83 1.3 0.37 2.0 0.12 2.3 0.37

Copper 16 6 log-censored 7.3 64 7.5 35 < 5.5 37 7.3

Dissolvedoxygen

16 7 log-censored 744 47253 810 18932 < 300 45700 735

Eh 16 0 normal 233 288 266 332 -18 354 217

Fluoride 10 0 log-normal 595 1020 490 3258 220 4090 490

Iron 16 0 log-normal 445 2102 145 20875 20 39594 205

Lead 16 0 log-normal 0.67 1.2 0.50 4.2 0.26 11 0.50

Lithium 16 4 log-censored 6.0 74 5.9 76 < 4.5 215 6.5

Magnesium 16 0 log-normal 16018 27970 11780 77945 4206 147192 13501

Manganese 16 0 log-normal 116 399 103 1191 2.8 2087 102

Molybdenum

16 12 log-censored 1.3 39 < 4.2 17 < 4.2 29 < 4.2

Nickel 16 10 log-censored 4.4 24 < 6.0 15 < 6.0 23 < 6.0

Nitrate-N 16 13 ins ins ins < 500 500 < 500 500 < 500

pH 16 0 normal 7.4 7.9 7.1 8.6 6.3 9.0 7.4

Phosphorus 16 6 log-censored 25 237 24 131 < 15 249 31

Potassium 16 0 normal 3087 4702 2007 7475 360 9766 2792

Table A. 4 continued.




No. valuescensored



Min Max StateMedian

Redox 16 0 normal 12 66 45 109 -237 131 3

Rubidium 16 15 ins ins ins < 555 608 < 555 732 < 555

Selenium 16 7 log-censored 0.70 80 1.1 95 < 1.0 308 2.0

Silicate 16 0 normal 8830 10471 8733 14667 5083 16249 8567

Silver 16 9 log-censored 0.0068 0.061 < 0.0090 0.036 < 0.0090 0.050 0.0090

Sodium 16 0 log-normal 14928 28054 8453 107935 3338 144848 9821

SpecificConductance

16 0 log-normal 200 440 240 680 5.0 1000 300

Strontium 16 0 log-normal 256 421 192 957 59 2077 197

Sulfate 16 0 no distribution - - 9765 400875 2340 1207380 3410

Sulfur 16 0 no distribution - - 3583 142756 1067 429506 3721

Temperature 16 0 normal 7.9 8.5 7.7 9.7 6.2 10 8.5

Thallium 16 11 log-censored 0.0073 0.011 < 0.0050 0.010 < 0.0050 0.010 < 0.0050

Titanium 16 10 log-censored 0.0018 0.058 < 0.0035 0.024 < 0.0035 0.049 < 0.0035


16 0 log-normal 302831 500726 194000 1209400 64000 2594000 257000

Total organiccarbon

16 1 log-censored 2757 19157 3450 9340 < 500 14100 2100

Totalphosphate-P

16 11 log-censored 12 128 < 20 69 < 20 90 < 20

Totalsuspended

solids

16 0 log-normal 5171 12850 4000 59000 1000 108000 4000

Vanadium 16 7 log-censored 4.9 30 5.5 19 4.7 35 5.1

Zinc 16 0 no distribution - - 8.9 380 3.1 517 15

Table A.5 : Descriptive statistics for undifferentiated Precambrian crystallineformations (PCUU).


No. valuescensored


Median 95hpercentile

Min Max StateMedian

ug/L ug/L


Aluminum 1 0 ins ins ins 1.5 ins - - < 0.060

Antimony 1 1 ins ins ins < 0.0080 ins - - < 0.0080


Barium 1 0 ins ins ins 1.7 ins - - 12

Beryllium 1 1 ins ins ins < 0.010 ins - - < 0.010

Boron 1 1 ins ins ins < 13 ins - - 271


Cadmium 1 1 ins ins ins < 0.020 ins - - < 0.020







No. valuescensored


Median 95hpercentile

Min Max StateMedian

Copper 1 0 ins ins ins 5.9 ins - - 5.9



Dissolvedoxygen

1 0 ins ins ins 9110 ins - - 1640





Lithium 1 0 ins ins ins 4.7 ins - - 20


Manganese 1 1 ins ins ins < 0.90 ins - - 241

Molybdenum 1 1 ins ins ins < 4.2 ins - - <4.2

Nickel 1 1 ins ins ins < 6.0 ins - - <6.0

Nitrate-N 1 1 ins ins ins < 500 ins - - <500


Phosphorus 1 1 ins ins ins < 15 ins - - 70


Redox 1 0 ins ins ins 2.0 ins - - -53

Rubidium 1 1 ins ins ins < 555 ins - - <555

Selenium 1 0 ins ins ins 2.0 ins - - 2.0


Silver 1 1 ins ins ins < 0.0090 ins - - <0.0090


SpecificConductance

1 0 ins ins ins 160 ins - - 162





Thallium 1 1 ins ins ins < 0.0050 ins - - <0.0050

Titanium 1 1 ins ins ins < 0.0035 ins - - <0.0035

Totaldissolved

solids

1 0 ins ins ins 136000 ins - - 666000

Total organiccarbon

1 0 ins ins ins 700 ins - - 3000

Totalphosphate-P

1 1 ins ins ins < 20 ins - - ins

Totalsuspended

solids

1 0 ins ins ins 2000 ins - - 4000

Vanadium 1 0 ins ins ins 5.5 ins - - 5.5

Zinc 1 0 ins ins ins 5.1 ins - - 8.0



Table A.6 : Descriptive statistics for the Biwabik Iron Formation (PEBI).


No. valuescensored



Min Max StateMedian

ug/L ug/L


Aluminum 1 0 ins ins ins 0.89 ins - - 0.89




Beryllium 1 0 ins ins ins 0.010 ins - - 0.010






Chromium 1 1 ins ins ins < 0.050 ins - - < 0.050


Copper 1 1 ins ins ins < 5.5 ins - - < 5.5

Dissolvedoxygen

1 1 ins ins ins < 300 ins - - < 300





Lithium 1 0 ins ins ins 7.0 ins - - 7.0



Molybdenum 1 1 ins ins ins < 4.2 ins - - < 4.2






Redox 1 0 ins ins ins -36 ins - - -36


Selenium 1 0 ins ins ins 4.5 ins - - 4.5


Silver 1 1 ins ins ins < 0.0090 ins - - < 0.0090


SpecificConductance

1 0 ins ins ins 290 ins - - 285





Thallium 1 1 ins ins ins < 0.0050 ins - - < 0.0050

Titanium 1 1 ins ins ins < 0.0035 ins - - < 0.0035

Totaldissolved

solids

1 0 ins ins ins 202000 ins - - 202000





No. valuescensored



Min Max StateMedian

Total organiccarbon

1 1 ins ins ins < 500 ins - - < 500

Totalphosphate-P

1 1 ins ins ins 20 ins - - < 20

Totalsuspended

solids

1 0 ins ins ins 2000 ins - - 2000

Vanadium 1 1 ins ins ins < 4.7 ins - - < 4.7

Zinc 1 0 ins ins ins 151 ins - - 151

Table A.7 : Descriptive statistics for Duluth Complex (PMDC).


No. valuescensored



Min Max StateMedian

ug/L ug/L


Aluminum 1 0 ins ins ins 771 ins - - 771



Barium 1 0 ins ins ins 2.0 ins - - 2.0

Beryllium 1 0 ins ins ins 0.39 ins - - 0.39








Copper 1 0 ins ins ins 79 ins - - 79

Dissolvedoxygen

1 0 ins ins ins 9100 ins - - 9100




Lead 1 0 ins ins ins 26 ins - - 26

Lithium 1 1 ins ins ins < 4.5 ins - - < 4.5



Molybdenum 1 0 ins ins ins 8.1 ins - - 8.1









No. valuescensored



Min Max StateMedian




Selenium 1 0 ins ins ins 14 ins - - 14


Silver 1 0 ins ins ins 0.050 ins - - 0.050


SpecificConductance

1 0 ins ins ins 320 ins - - 320





Thallium 1 1 ins ins ins < 0.0050 ins - - < 0.0050

Titanium 1 0 ins ins ins 0.064 ins - - 0.064

Totaldissolved

solids

1 0 ins ins ins 186000 ins - - 186000

Total organiccarbon

1 0 ins ins ins 900 ins - - 900

Totalphosphate-P

1 0 ins ins ins 60 ins - - 60

Totalsuspended

solids

1 0 ins ins ins 86000 ins - - 86000

Vanadium 1 1 ins ins ins < 4.7 ins - - < 4.7


Table A.8 : Descriptive statistics for the Mount Simon-Fond du Lac Formation(PMFL).


No. valuescensored



Min Max StateMedian

ug/L ug/L

Alkalinity 1 0 ins ins ins 223000 ins - - ins

Aluminum 1 0 ins ins ins 174 ins - - ins

Antimony 1 0 ins ins ins 0.050 ins - - ins

Arsenic 1 0 ins ins ins 1.1 ins - - ins

Barium 1 0 ins ins ins 104 ins - - ins

Beryllium 1 0 ins ins ins 0.020 ins - - ins

Boron 1 0 ins ins ins 30 ins - - ins

Bromide 1 1 ins ins ins < 0.20 ins - - ins

Cadmium 1 0 ins ins ins 0.41 ins - - ins

Calcium 1 0 ins ins ins 58420 ins - - ins

Chloride 1 0 ins ins ins 1020 ins - - ins

Chromium 1 0 ins ins ins 5.0 ins - - ins

Cobalt 1 0 ins ins ins 0.31 ins - - ins

Copper 1 0 ins ins ins 48 ins - - ins



No. valuescensored



Min Max StateMedian

Dissolved oxygen 1 1 ins ins ins < 300 ins - - ins

Eh 1 0 ins ins ins 222 ins - - ins




Iron 1 0 ins ins ins 631 ins - - ins

Lead 1 0 ins ins ins 15 ins - - ins

Lithium 1 1 ins ins ins < 4.5 ins - - ins

Magnesium 1 0 ins ins ins 19695 ins - - ins

Manganese 1 0 ins ins ins 4.5 ins - - ins

Molybdenum 1 1 ins ins ins < 4.2 ins - - ins

Nickel 1 1 ins ins ins < 6.0 ins - - ins

Nitrate-N 1 1 ins ins ins < 500 ins - - ins

pH 1 0 ins ins ins 7.5 ins - - ins

Phosphorus 1 1 ins ins ins < 15 ins - - ins

Potassium 1 0 ins ins ins 1390 ins - - ins

Redox 1 0 ins ins ins 0 ins - - ins

Rubidium 1 1 ins ins ins < 555 ins - - ins

Selenium 1 0 ins ins ins 5.9 ins - - ins

Silicate 1 0 ins ins ins 11069 ins - - ins

Silver 1 0 ins ins ins 0.12 ins - - ins

Sodium 1 0 ins ins ins 5884 ins - - ins

SpecificConductance

1 0 ins ins ins 430 ins - - ins

Strontium 1 0 ins ins ins 60 ins - - ins

Sulfate 1 0 ins ins ins 14700 ins - - ins

Sulfur 1 0 ins ins ins 5232 ins - - ins

Temperature 1 0 ins ins ins 7.5 ins - - ins

Thallium 1 0 ins ins ins 0.010 ins - - ins

Titanium 1 0 ins ins ins 0.014 ins - - ins



Total organiccarbon


Total phosphate-P

1 1 ins ins ins < 20 ins - - ins



Vanadium 1 0 ins ins ins 5.1 ins - - ins

Zinc 1 0 ins ins ins 196 ins - - ins



Table A.9 : Descriptive statistics for the Mount Simon-Hinckley Formation(PMHN).


No. valuescensored



Min Max StateMedian

ug/L ug/L


Aluminum 1 0 ins ins ins 7.0 ins - - 3.2




Beryllium 1 1 ins ins ins < 0.010 ins - - <0.010

Boron 1 0 ins ins ins 51 ins - - <13

Bromide 1 1 ins ins ins < 0.20 ins - - <0.20

Cadmium 1 1 ins ins ins < 0.020 ins - - <0.020





Copper 1 0 ins ins ins 13 ins - - <5.5

Dissolvedoxygen

1 1 ins ins ins < 300 ins - - <300




Lithium 1 0 ins ins ins 12 ins - - <4.5



Molybdenum 1 0 ins ins ins 4.4 ins - - <4.2

Nickel 1 0 ins ins ins 9.2 ins - - <6.0

Nitrate-N 1 1 ins ins ins < 500 ins - - <500





Rubidium 1 0 ins ins ins 713 ins - - <555

Selenium 1 1 ins ins ins < 1.0 ins - - <1.0


Silver 1 0 ins ins ins 0.020 ins - - <0.0090


SpecificConductance

1 0 ins ins ins 250 ins - - 248





Thallium 1 0 ins ins ins 0.040 ins - - <0.0050

Titanium 1 0 ins ins ins 0.0054 ins - - <0.0035

Totaldissolved

solids

1 0 ins ins ins 152000 ins - - 150000





No. valuescensored



Min Max StateMedian

Total organiccarbon

1 0 ins ins ins 2700 ins - - 2700

Total phosphate-P 1 0 ins ins ins 20 ins - - 20


1 0 ins ins ins 3000 ins - - 4000

Vanadium 1 0 ins ins ins 12 ins - - 6.1


Table A.10 : Descriptive statistics for the North Shore Volcanics group (PMNS).


No. valuescensored



Min Max StateMedian

ug/L ug/L ug/L ug/L ug/L ug/L ug/L

Alkalinity 12 0 normal 135500 174249 119500 210700 66000 217000 125500

Aluminum 12 0 log-normal 45 216 49 1414 1.1 1448 37



Barium 12 3 log-censored 5.2 62 5.6 34 < 1.4 41 7.0

Beryllium 12 4 log-censored 0.018 2.1 0.025 1.8 < 0.010 2.5 0.020


Bromide 12 11 ins ins ins < 0.20 0.50 < 0.20 0.67 < 0.20

Cadmium 12 6 log-censored 0.041 0.19 0.020 0.12 < 0.020 0.13 0.030

Calcium 12 0 normal 27843 38162 23723 50769 1801 55204 26763


Chromium 12 3 log-censored 0.57 11 0.63 5.6 < 0.050 5.9 0.66

Cobalt 12 0 nodistribution

- - 0.27 3.5 0.10 4.0 0.29

Copper 12 4 log-censored 9.5 151 8.0 73 < 5.5 79 12

Dissolved oxygen 12 7 log-censored 480 43736 < 300 10390 < 300 10690 < 300

Eh 12 0 normal 158 223 184 267 13 269 173

Fluoride 8 0 normal 805 1174 715 1596 270 1600 430

Iron 12 0 log-normal 266 1100 204 19929 9.6 26320 238

Lead 12 0 log-normal 0.50 1.4 0.39 13 0.060 16 0.38

Lithium 12 5 log-censored 6.1 50 5.8 35 < 4.5 44 11

Magnesium 12 0 normal 11654 17226 9555 21840 793 22091 11528


Molybdenum 12 7 log-censored 5.6 20 < 4.2 14 < 4.2 15 < 4.2



pH 12 0 normal 8.3 8.7 8.0 9.2 7.0 9.3 8.0


Potassium 12 2 log-censored 686 3651 674 2881 < 119 3540 776

Redox 12 0 normal -64 0.62 -38 43 -209 46 -42







No. valuescensored



Min Max StateMedian

Silicate 12 0 normal 8678 11642 8296 16192 4637 16766 9039

Silver 12 3 log-censored 0.017 0.27 0.018 0.19 < 0.0090 0.24 0.013


SpecificConductance

12 0 log-normal 300 420 270 840 160 950 339

Strontium 12 0 log-normal 112 206 111 493 11 611 121

Sulfate 12 0 log-normal 11174 251134 9150 188817 1800 247290 2930

Sulfur 12 0 log-normal 4142 9014 3258 67289 898 88252 3390

Temperature 12 0 normal 7.3 7.8 7.2 8.4 6.0 8.6 7.8

Thallium 12 8 log-censored 0.0061 0.012 <0.0050

0.010 < 0.0050 0.010 < 0.0050

Titanium 12 5 log-censored 0.0035 0.28 0.0039 0.17 < 0.0035 0.23 0.0050


12 0 normal 245400 351507

172000 528200 108000 614000 238000

Total organiccarbon

12 0 nodistribution

- - 1000 5700 900 5700 1300

Total phosphate-P 12 7 log-censored 7.5 728 < 20 256 < 20 280 < 20


12 0 nodistribution

- - 4500 218600 2000 230000 4000

Vanadium 12 4 log-censored 6.1 27 6.4 22 < 4.7 23 6.5

Zinc 12 1 log-censored 11 214 11 271 < 2.7 370 13

Table A.11 : Descriptive statistics for undifferentiated Proterozoic Metasedimentary units(PMUD).


No. valuescensored



Min Max StateMedian


Alkalinity 19 0 normal 171421 209259 160000 ins 47000 330000 159500

Aluminum 20 1 log-censored 6.5 197 4.2 2217 < 0.060 2330 3.9


Arsenic 20 4 log-censored 1.0 16 1.6 8.2 < 0.060 8.3 1.1

Barium 20 2 log-censored 30 348 37 207 < 1.4 209 42

Beryllium 20 10 log-censored 0.0059 0.17 < 0.010 0.35 < 0.010 0.37 < 0.010



Cadmium 20 12 log-censored 0.025 0.33 < 0.020 0.25 < 0.020 0.25 < 0.020

Calcium 20 0 normal 35392 46722 31662 82000 539 82499 31704

Chloride 20 0 nodistribution

- - 2275 4779162 470 5029000 1850


Cobalt 20 1 log-censored 0.27 4.6 0.21 5.0 < 0.0020 5.1 0.22

Copper 20 9 log-censored 9.2 62 7.2 39 < 5.5 39 6.8

Eh 20 0 normal 183 238 224 333 -57 333 216

Fluoride 14 0 normal 448 569 400 ins 200 890 350

Iron 20 0 log-normal 297 680 298 11407 12 11763 209





No. valuescensored



Min Max StateMedian

Lead 20 0 log-normal 0.41 0.80 0.42 8.4 0.050 8.7 0.47

Lithium 20 8 log-censored 4.9 53 5.2 49 < 4.5 50 5.0



Molybdenum 20 14 log-censored 3.7 11 < 4.2 9.9 < 4.2 10 < 4.2


Nitrate-N 20 18 log-censored 16 2534 < 500 1930 < 500 2000 < 500

pH 19 0 normal 7.7 8.0 7.6 ins 6.1 9.1 7.6



Redox 19 0 normal -39 16 0 ins -279 112 -1.0

Rubidium 20 20 ins ins ins < 555 ins < 555 555 < 555


Silicate 20 0 normal 8624 9898 8757 13650 2921 13669 8688

Silver 20 10 log-censored 0.011 0.14 0.0090 0.12 < 0.0090 0.12 < 0.0090


SpecificConductance

19 0 normal 330 410 320 ins 56 690 330

Strontium 20 0 normal 217 320 124 850 1.0 872 125

Sulfate 20 2 log-censored 5034 73806 5805 50201 < 300 50220 1950

Sulfur 20 1 log-censored 1830 28677 2195 16777 < 22 16781 2374

Temperature 19 0 normal 7.6 7.9 7.6 ins 6.7 8.7 7.7

Thallium 20 15 log-censored 0.0041 0.042 <0.0050

0.030 < 0.0050 0.030 < 0.0050

Titanium 20 14 log-censored 0.00074 0.039 <0.0035

0.064 < 0.0035 0.067 < 0.0035


20 0 normal 224211 266489 216000 432700 90000 438000 222000

Total organiccarbon

20 2 log-censored 2004 7525 2000 5480 < 500 5500 1700

Total phosphate-P 20 11 log-censored 15 288 < 20 263 < 20 270 20


20 0 nodistribution

- - 4000 141200 1000 148000 4000

Vanadium 20 13 log-censored 3.8 21 < 4.7 20 < 4.7 20 < 4.7

Zinc 20 1 log-censored 13 134 12 271 < 2.7 278 11



Table A.12 : Descriptive statistics for buried Quaternary artesian aquifers (QBAA).


No. valuescensored



Min Max StateMedian




Antimony 52 27 log-censored 0.012 0.093 < 0.0080 0.067 < 0.0080 0.091 0.011


Barium 52 0 normal 62 73 57 131 2.7 189 61



Bromide 52 52 ins ins ins < 0.20 . < 0.20 0.1 < 0.20


Calcium 52 0 log-normal 38177 47152 34432 97273 222 108918 79537



Cobalt 52 0 log-normal 0.33 0.45 0.32 1.7 0.020 2.6 0.46

Copper 52 33 log-censored 2.0 99 < 5.5 55 < 5.5 530 < 5.5

Dissolved oxygen 52 46 log-censored 42 11563 < 300 5496 < 300 28300 < 300

Eh 52 0 log-normal 277 287 197 312 -28 318 158

Fluoride 32 0 normal 432 495 400 759 200 1110 380

Iron 52 1 log-censored 344 11731 502 4227 < 3.2 20207 1179

Lead 52 4 log-censored 0.24 5.3 0.21 4.9 < 0.030 25 0.18

Lithium 52 26 log-censored 4.8 33 4.5 27 < 4.5 51 14

Magnesium 52 0 log-normal 17426 22553 13773 43987 180 64521 30515

Manganese 52 1 log-censored 84 1385 89 750 < 0.90 1462 131



Nitrate-N 52 47 log-censored 173 792 < 500 700 < 500 1000 < 500

pH 51 0 normal 7.7 7.8 7.8 8.5 6.2 8.5 7.3


Potassium 52 0 log-normal 1982 2569 1889 5500 274 7542 3068

Redox 51 0 log-normal 52 64 -26 92 -248 96 -56

Rubidium 52 49 log-censored 361 670 < 555 622 < 555 746 < 555

Selenium 52 13 log-censored 1.8 11 1.9 9.3 < 1.0 11 2.4

Silicate 52 0 normal 8836 9545 8803 13424 4935 13612 11914

Silver 52 30 log-censored 0.0096 0.088 < 0.0090 0.080 < 0.0090 0.11 < 0.0090


SpecificConductance

51 0 normal 340 390 300 700 2 770 619

Strontium 52 0 log-normal 144 205 135 728 1.5 1000 304


Sulfur 52 0 log-normal 3032 4683 2849 31182 113 130743 8110

Temperature 51 0 normal 8.0 8.2 7.8 9.6 6.4 11 8.9

Thallium 52 38 log-censored 0.0052 0.031 < 0.0050 0.030 < 0.0050 0.032 < 0.0050



52 0 normal 266980 309180 240000 497600 96000 1010000 430000

Total organiccarbon

52 0 log-normal 1782 2314 2000 7645 700 12000 2600



Table A. 12 continued.


No. valuescensored



Min Max StateMedian

Total phosphate-P

52 12 log-censored 39 342 35 221 < 20 320 60


52 0 log-normal 4557 7186 4000 34900 1000 112000 5000


Zinc 52 5 log-censored 10 160 8.3 329 < 2.7 1102 13

Table A.13 : Descriptive statistics for unconfined buried Quaternary aquifers (QBUA).


No. valuescensored



Min Max StateMedian




Antimony 12 9 log-censored 0.013 0.057 < 0.0080 0.040 < 0.0080 0.040 0.016

Arsenic 12 1 log-censored 1.5 22 2.2 8.6 < 0.060 9.1 1.9

Barium 12 0 normal 74 108 54 177 1.6 191 71





Calcium 12 0 normal 46120 65663 46994 100875 155 115508 78821


Chromium 12 0 log-normal 0.45 1.0 0.49 4.3 0.090 4.7 0.69

Cobalt 12 0 normal 0.28 0.39 0.32 0.56 0.050 0.63 0.46

Copper 12 7 log-censored 6.3 29 < 5.5 20 < 5.5 22 < 5.5

Dissolvedoxygen

12 10 log-censored 42 26955 < 300 6956 < 300 9230 < 500

Eh 12 0 normal 186 238 214 290 71 295 220

Fluoride 4 0 normal 320 424 290 ins 200 570 305

Iron 12 0 log-normal 448 1905 464 7390 7 7816 367

Lead 12 2 log-censored 0.17 1.4 0.14 1.5 < 0.030 2.0 0.19

Lithium 12 8 log-censored 5.6 15 < 4.5 12 < 4.5 13 7.1


Manganese 12 0 normal 282 512 157 1038 0.90 1248 152




pH 12 0 normal 7.4 7.8 7.4 70 6.0 8.4 7.2

Phosphorus 12 2 log-censored 61 414 86 8.3 < 15 202 57


Redox 12 0 normal -34 18 -5.5 2555 -149 74 5


Selenium 12 2 log-censored 2.3 5.8 2.4 4.4 < 1.0 4.7 3.2

Silicate 12 0 normal 10198 12794 10130 18051 3331 20396 10867





No. valuescensored



Min Max StateMedian

Silver 12 8 log-censored 0.011 0.065 < 0.0090 0.044 < 0.0090 0.050 < 0.0090

Sodium 12 0 no distribution - - 4525 120410 1688 168649 5906

SpecificConductance

12 0 normal 350 500 360 750 38 780 533

Strontium 12 0 normal 81 110 85 139 0.90 139 112


Sulfur 12 0 normal 1732 2862 1501 4951 401 5364 5406

Temperature 12 0 no distribution - - 8.2 11 7.4 12 8.8

Thallium 12 11 ins ins ins < 0.0050 0.0080 < 0.0050 0.010 < 0.0050


Totaldissolved

solids

12 0 normal 245000 326715 223000 471200 28000 482000 350000

Total organiccarbon

12 1 log-censored 2684 23591 2500 18850 < 500 21700 1900

Totalphosphate-P

12 4 log-censored 57 390 60 201 < 20 210 40

Totalsuspended

solids

12 0 log-normal 3631 6817 3000 16000 1000 16000 2000


Zinc 12 2 log-censored 9.0 133 8.0 106 < 2.7 138 12



Table A.14 : Descriptive statistics for Quaternary water table aquifers (QWTA).


No. valuescensored



Min Max StateMedian

ug/L ug/L ug/L ug/L ug/L ug/L ug/LAlkalinity 21 0 normal 143238 172460 128000 287300 31000 290000 237500Aluminum 21 1 log-censored 8.4 745 5.3 750 < 0.060 756 1.2Antimony 21 10 log-censored 0.011 0.065 0.010 0.075 < 0.0080 0.080 0.017Arsenic 21 3 log-censored 1.0 20 1.8 17 < 0.060 19 1.3Barium 21 0 normal 55 73 38 143 2.9 145 85

Beryllium 21 6 log-censored 0.015 0.19 0.010 0.12 < 0.010 0.12 < 0.010Boron 21 4 log-censored 21 96 18 80 < 13 82 24

Bromide 21 21 ins ins ins < 0.20 ins < 0.20 0.10 < 0.20Cadmium 21 12 log-censored 0.040 0.21 < 0.020 0.18 < 0.020 0.19 < 0.020Calcium 21 0 normal 35569 43709 32346 65444 99 65513 74237Chloride 21 0 log-normal 1537 2744 1160 19679 330 20050 5810

Chromium 21 3 log-censored 0.28 6.3 0.25 4.8 < 0.050 5.0 0.55Cobalt 21 0 log-normal 0.34 0.55 0.34 2.4 0.020 2.5 0.48Copper 21 8 log-censored 6.2 71 6.6 128 < 5.5 140 6.3

Dissolvedoxygen

21 18 log-censored 24 11886 < 300 6525 < 300 6590 < 500

Eh 21 0 normal 178 221 186 298 -34 298 187Fluoride 7 0 normal 338 416 310 ins 200 620 300

Iron 21 0 log-normal 728 1779 726 13515 41 13774 811Lead 21 3 log-censored 0.21 18 0.17 10 < 0.030 11 0.18

Lithium 21 7 log-censored 5.6 18 5.3 16 < 4.5 17 5.7Magnesium 21 0 normal 12160 15969 10147 36349 121 37601 22224Manganese 21 1 log-censored 89 3101 90 994 < 0.90 1011 176

Molybdenum 21 17 log-censored 1.9 14 < 4.2 12 < 4.2 12 < 4.2Nickel 21 13 log-censored 6.8 18 < 6.0 18 < 6.0 18 < 6.0

Nitrate-N 21 19 log-censored 1.5 5497 < 500 3750 < 500 4100 < 500pH 21 0 normal 7.5 7.8 7.6 8.4 6.1 8.4 7.2

Phosphorus 21 1 log-censored 49 403 38 427 < 15 441 56Potassium 21 1 log-censored 1333 6040 1301 5179 < 119 5288 1766

Redox 21 0 normal -43 -0.49 -35 77 -251 77 -24Rubidium 21 19 log-censored 227 857 < 555 795 < 555 817 < 555Selenium 21 11 log-censored 1.1 10 < 1.0 8.6 < 1.0 9.0 2.1Silicate 21 0 log-normal 10069 11572 9449 22295 6611 23012 10819Silver 21 13 log-censored 0.016 0.040 < 0.0090 0.039 < 0.0090 0.040 < 0.0090

Sodium 21 0 log-normal 5358 7681 4275 75862 2324 83019 4986Specific

Conductance21 0 normal 250 310 240 530 2.0 540 465

Strontium 21 0 log-normal 68 112 78 414 1.3 436 105Sulfate 21 5 log-censored 7066 38424 10440 20256 < 300 20520 4250Sulfur 21 0 normal 3303 4446 3845 7357 100 7427 4603

Temperature 21 0 normal 8.1 8.6 8.1 11 5.8 11 8.8Thallium 21 15 log-censored 0.0073 0.011 < 0.0050 0.010 < 0.0050 0.010 < 0.0050Titanium 21 11 log-censored 0.0031 0.051 < 0.0035 0.045 < 0.0035 0.047 < 0.0035


21 0 normal 196476 233155 168000 354800 68000 356000 340000

Total organiccarbon

21 0 log-normal 2211 3356 2000 14550 600 15100 2400





No.values

censored



Min Max StateMedian

Totalphosphate-P

21 9 log-censored 21 909 20 942 < 20 1020 40


21 0 log-normal 4982 8221 4000 29600 1000 30000 4000

Vanadium 21 9 log-censored 6.0 15 5.8 12 < 4.7 12 5.4Zinc 21 3 log-censored 7.7 50 8.0 71 < 2.7 76 12

Table A.15 : Coefficients for log-censored data from analysis of descriptive statistics,for each aquifer and chemical. See MPCA, 1998a, for application of thesecoefficients.

ChemicalParameter

PCCR PMNS PMUD QBAA QBUA QWTA

a b a b a b a b a b a bAluminum - - - - 1.865 1.743 1.376 2.049 0.512 1.596 2.125 2.29Antimony -4.082 1.038 -3.46 1.119 -3.977 1.068 -4.434 1.048 -4.327 0.743 -4.535 0.916Arsenic -0.35 1.877 -0.289 1.454 0.046 1.403 0.687 1.328 0.426 1.369 -0.004 1.521Barium - - 1.644 1.27 3.403 1.25 - - - - - -

Beryllium -3.988 1.549 -4.039 2.435 -5.129 1.713 -4.991 1.187 -5.133 2.631 -4.214 1.314Boron 3.891 1.281 5.206 1.573 3.801 1.375 3.64 1.243 2.924 0.54 3.037 0.779

Cadmium -3.667 1.764 -3.201 0.782 -3.693 1.321 -4.122 1.334 -3.868 1.246 -3.213 0.834Chromium -0.795 1.122 -0.557 1.512 -1.504 1.544 -1.408 1.666 - - -1.281 1.591

Cobalt - - - - -1.317 1.454 - - - - - -Copper 1.99 1.105 2.253 1.409 2.22 0.97 0.71 1.98 1.836 0.776 1.827 1.245

Dissolvedoxygen

6.612 2.118 6.174 2.302 6.09 1.062 3.748 2.861 3.73 3.302 3.164 3.173

Iron - - - - - - 5.842 1.8 - - - -Lead - - - - - - -1.427 1.579 -1.793 1.079 -1.56 2.262

Lithium 1.787 1.281 1.812 1.068 1.59 1.216 1.577 0.987 1.718 0.509 1.715 0.611Manganese - - - - - - 4.431 1.43 - - 4.494 1.809

Molybdenum 0.298 1.715 1.724 0.639 1.312 0.554 1.274 0.666 0.762 0.927 0.659 1.023Nickel 1.479 0.864 1.176 1.232 1.796 0.594 1.28 0.709 1.797 0.601 1.91 0.492

Nitrate-N - - - - 2.763 2.589 5.153 0.776 - - 0.431 4.174Phosphorus 3.22 1.147 2.941 1.56 3.489 0.997 3.901 0.94 4.118 0.974 3.889 1.077Potassium - - 6.531 0.853 - - - - - - 7.195 0.771Rubidium - - - - - - 5.89 0.315 - - 5.425 0.678Selenium -0.355 2.419 0.242 1.379 0.69 1.481 0.604 0.895 0.818 0.481 0.075 1.138

Silver -4.985 1.119 -4.087 1.426 -4.531 1.326 -4.65 1.132 -4.493 0.894 -4.141 0.476Sulfate - - - - 8.524 1.37 8.83 1.286 7.549 1.552 8.863 0.864Sulfur - - - - 7.512 1.404 - - - - - -

Thallium -4.915 0.206 -5.106 0.366 -5.498 1.187 -5.255 0.915 - - -4.916 0.205




ChemicalParameter


a b a b a b a b a b a bTitanium -6.312 1.77 -5.66 2.241 -7.204 2.021 -6.334 1.152 -5.426 0.462 -5.781 1.428

Total organiccarbon

7.922 0.989 - - 7.603 0.675 - - 7.895 1.109 - -

Total phosphate-P 2.486 1.206 2.016 2.334 2.723 1.5 3.67 1.104 4.048 0.979 3.033 1.928Vanadium 1.589 0.932 1.814 0.752 1.342 0.871 1.645 0.478 1.631 0.593 1.793 0.463

Zinc - - 2.369 1.529 2.573 1.186 2.346 1.39 2.193 1.375 2.041 0.954

Table A.16 : Coefficients for log-normal data from analysis of descriptive statistics,for eachaquifer and chemical. See MPCA, 1998a, for application of thesecoefficients.

ChemicalParameter


std. dev. n std. dev. n std. dev. n std. dev. n std. dev. n std. dev. nAlkalinity 0.2940 16 - - - - - - - - - -

Aluminum 0.7351 16 1.079 12 - - - - - - - -

Barium 0.3698 16 - - - - - - - - - -

Calcium 0.3776 16 - - - - 0.3791 52 - - - -

Chloride 0.5901 16 0.7824 12 - - 0.6234 52 0.4951 12 0.5532 21

Chromium - - - - - - - - 0.5472 12 - -

Cobalt - - - - - - 0.3796 52 - - 0.4789 21

Eh - - - - - - 0.4660 52 - - - -

Fluoride 0.3869 13 - - - - - - - - - -

Iron 1.079 16 0.9710 12 0.7679 20 - - 0.9888 12 0.8524 21

Lead 0.3869 16 0.7153 12 0.6073 20 - - - - - -

Magnesium 0.3916 16 - - - - 0.3684 52 - - - -

Manganese 0.8942 16 0.5963 12 0.9338 20 - - - - - -

Potassium - - - - - - 0.2839 52 - - - -

Redox - - - - - - 0.4280 51 - - - -

Silicate - - - - - - - - - - 0.1327 21

Sodium 0.5022 16 0.4546 12 0.4380 20 0.4684 52 - - 0.3434 21

Specific Conductance 0.5062 16 0.2293 12 - - - - - - - -

Strontium 0.3719 16 0.4200 12 - - 0.4252 52 - - 0.4784 21

Sulfate - - 0.5536 12 - - - - - - - -

Sulfur - - 0.5315 12 - - 0.5443 52 - - - -

Total dissolved solids 0.3797 16 - - - - - - - - - -




ChemicalParameter


std. dev. n std. dev. n std. dev. n std. dev. n std. dev. n std. dev. nTotal organic

carbon- - - - - - 0.3142 52 - - 0.3981 21


0.6134 16 - - - - 0.4468 52 0.4307 12 0.4779 21

Table A.17 : Median concentrations, in ug/L, of sampled chemicals for each of themajor aquifers. The p-value indicates the probability that aquifers have equalconcentrations.

Chemical p-value PCCR PMNS PMUD QBAA QBUA QWTA

ug/L ug/L ug/L ug/L ug/L ug/L ug/LAlkalinity 0.051 135500 119500 160000 198000 189000 128000Aluminum 0.002 13 49 4.2 2.8 1.3 5.3Antimony 0.011 0.018 0.040 0.020 < 0.0080 < 0.0080 0.010Arsenic 0.028 0.64 0.97 1.6 2.3 2.2 1.8Barium < 0.001 38 5.6 37 57 54 38

Beryllium 0.062 0.020 0.025 0.0075 < 0.010 < 0.010 0.010Boron < 0.001 49 219 37 43 18 18

Bromide 0.073 < 0.20 < 0.20 < 0.20 < 0.20 < 0.20 < 0.20Cadmium 0.794 0.020 0.020 < 0.020 < 0.020 < 0.020 < 0.020Calcium 0.167 31747 23723 31662 34432 46994 32346Chloride 0.169 3220 2445 2275 1630 660 1160

Chromium 0.587 0.49 0.63 0.26 0.28 0.49 0.25Cobalt 0.639 0.37 0.27 0.21 0.32 0.32 0.34Copper 0.137 7.5 8.0 7.2 < 5.5 < 5.5 6.6

Dissolvedoxygen

0.005 810 < 300 < 300 < 300 < 300 < 300

Eh 0.438 266 184 224 197 214 186Fluoride 0.021 490 715 400 400 290 310

Iron 0.697 145 204 298 502 464 726Lead 0.025 0.50 0.39 0.42 0.21 0.14 0.17

Lithium 0.646 5.9 5.8 5.2 4.5 < 4.5 5.3Magnesium 0.154 11780 9555 12797 13773 10502 10147Manganese 0.228 103 35 70 89 157 90

Molybdenum 0.747 < 4.2 < 4.2 < 4.2 < 4.2 < 4.2 < 4.2Nickel 0.633 < 6.0 < 6.0 < 6.0 < 6.0 < 6.0 < 6.0

Nitrate-N 0.961 < 500 < 500 < 500 < 500 < 500 < 500pH 0.440 7.1 8.0 7.6 7.8 7.4 7.6

Phosphorus 0.117 24 21 32 51 86 38Potassium 0.058 2007 674 1489 1889 1430 1301

Redox 0.005 45 -38 0 -26 -5.5 -35Rubidium 0.853 < 555 < 555 < 555 < 555 < 555 < 555Selenium 0.213 1.1 1.4 2.0 1.9 2.4 < 1.0




Chemical p-value PCCR PMNS PMUD QBAA QBUA QWTA

Silicate 0.298 8733 8296 8757 8803 10130 9449Silver 0.369 < 0.0090 0.018 0.0090 < 0.0090 < 0.0090 < 0.0090

Sodium 0.001 8453 18686 10163 9638 4525 4275Specific

Conductance0.524 0.24 0.27 0.32 0.30 0.36 0.24

Strontium 0.002 192 111 124 135 85 78Sulfate 0.076 9765 9150 5805 7290 2655 10440Sulfur 0.108 3583 3258 2195 2849 1501 3845

Temperature 0.009 7.7 7.2 7.6 7.8 8.2 8.1Thallium 0.801 < 0.0050 < 0.0050 < 0.0050 < 0.0050 < 0.0050 < 0.0050Titanium 0.161 < 0.0035 0.0039 < 0.0035 < 0.0035 < 0.0035 < 0.0035


0.405 194000 172000 216000 240000 223000 168000

Total organiccarbon

0.199 3450 1000 2000 2000 2500 2000

Totalphosphate-P

0.011 < 20 < 20 < 20 35 60 20

Totalsuspended

solids

0.848 4000 4500 4000 4000 3000 4000

Vanadium 0.531 5.5 6.4 < 4.7 < 4.7 < 4.7 5.8Zinc 0.791 8.9 11 12 8.3 8.0 8.0

Table A.18 : Median concentrations of chemicals in buried Quaternary andPrecambrian bedrock aquifers. An asterisk indicates chemicals for whichconcentrations differed between the two aquifer groups. Concentrations are in ug/Lexcept for pH, temperature (oF), specific conductance (umhos/cm), and Eh (mV).

Chemical Precambrian Buried Quaternary

Alkalinity 141000 * 198000Aluminum 7.0 * 2.6Antimony 0.03 * < 0.0080Arsenic 0.99 * 2.3Barium 23 * 56

Beryllium 0.010 * < 0.010Boron 52 * 26

Cadmium < 0.020 < 0.020Calcium 30801 * 37074Cesium 0.040 * < 0.010Chloride 2190 975

Chromium 0.43 0.28Cobalt 0.26 0.32Copper 7.5 * 5.4

Dissolved oxygen < 300 * < 300




Chemical Precambrian Buried QuaternaryEh 223 201

Fluoride 425 370Iron 206 484Lead 0.47 * 0.20

Lithium 5.7 4.4Magnesium 11466 * 13520Manganese 55 89

Molybdenum < 4.2 < 4.2Nickel < 6.0 < 6.0

Nitrate-N < 500 < 500pH 7.80 7.70

Phosphorus 24 * 53Potassium 1390 * 1743Rubidium < 555.5 < 555.5Selenium 1.9 2.1Silicate 8460 9237Silver 0.01 < 0.0090

Sodium 10085 7341Specific Conductance 272 303

Strontium 136 123Sulfate-S 2610 2125

Sulfur 2773 2526Temperature 7.55 * 7.9

Thallium < 0.0050 < 0.0050Tin < 0.080 < 0.080

Titanium < 0.0035 < 0.0035Total dissolved solids 200000 235000Total organic carbon 1700 2050Total phosphate-P 10 * 40

Total suspended solids 4000 4000Vanadium 5.1 4.6

Zinc 13 8.3Zirconium 0.090 0.050



Table A.19 : Summary of water quality criteria, basis of criteria, and endpoints, bychemical parameter.

Chemical Criteria (ug/L) Basis of criteria EndpointAlkalinity - - -Aluminum (Al) 50 MCL -Antimony (Sb) 6 HRL -Arsenic (As) 50 MCL CancerBarium (Ba) 2000 HRL Cardiovascular/bloodBeryllium (Be) 0.08 HRL CancerBoron (B) 600 HRL ReproductiveBromide (Br) - - -Cadmium (Cd) 4 HRL KidneyCalcium (Ca) - - -Chloride (Cl) 250000 SMCL -Chromium (Cr) 200001 HRL -Cobalt (Co) 30 HBV -Copper (Cu) 1000 HBV -Dissolved Oxygen - - -Fluoride (F) 4000 MCL -Iron (Fe) 300 SMCL -Lead (Pb) 15 Action level at tap -Lithium (Li) - - -Magnesium (Mg) - - -Manganese (Mn) 100 (1000)2 HRL Central nervous systemMercury (Hg) 2 MCL -Molybdenum (Mo) 30 HBV KidneyNickel (Ni) 100 HRL -Nitrate-N (NO3-N) 10000 HRL Cardiovascular/bloodOrtho-phosphate - - -pH - - -Phosphorustotal - - -Potassium (K) - - -Redox/Eh - - -Rubidium (Rb) - - -Selenium (Se) 30 HRL -Silicate (Si) - - -Silver (Ag) 30 HRL -Sodium (Na) 250000 SMCL -Specific Conductivity - - -Strontium (Sr) 4000 HRL BoneSulfate (SO4) 500000 MCL -Sulfur (S) - - -Temperature - - -Thallium (Tl) 0.6 HRL Gastrointestinal/liverTitanium (Ti) - - -Total dissolved solids - - -Total organic carbon - - -Total phosphate - - -




Chemical Criteria (ug/L) Basis of criteria EndpointTotal suspended solids - - -Vanadium (V) 50 HRL -Zinc (Zn) 2000 HRL -1,1,1-trichloroethane 600 HRL Gastrointestinal/liver1,1-dichloroethane 70 HRL kidney1,1-dichloroethene 6 HRL Gastrointestinal/liver1,2-dichloroethane 4 HRL cancer1,2-dichloropropane 5 HRL canceracetone 700 HRL cardiovascular/blood; liverbenzene 10 HRL cancerbromodichloromethane

6 HRL cancer

chlorodibromomethane

- - -

chloroform 60 HRL cancerdichlorodifluoromethane

1000 HRL body weight

dichlorofluoromethane - - -ethyl ether 1000 HRL body weightisopropylbenzene - - -xylene 10000 HRL nervous systemmethyl ethyl ketone 4000 HRL reproductivemethylene chloride 50 HRL cancernaphthalene 300 HRL cardiovascular/bloodtetrachloroethene 7 HRL cancertetrahydrofuran 100 HRL Gastrointestinal/livertoluene 1000 HRL kidney;

gastrointestinal/livertrichloroethene 30 HRL cancer1,2,4-trimethylbenzene

- - -

1,3,5-trimethylbenzene

- - -

cis-1,2 dichloroethene 70 HRL cardiovascular/bloodethyl benzene 700 HRL kidney;

gastrointestinal/livern-butylbenzene - - -n-propyl benzene - - -p-isopropyltoluene - - -styrene - - -trichlorofluoromethane

- - -

1 Trivalent chromium2 The current HRL for manganese is 100, but calculations were made using a value of1000 ug/L (MDH, 1997)



Table A.20 : Number of samples exceeding health-based water quality criteria, byaquifer.

Number exceedances of criteriaChemical PCCR PMDC PMFL PMNS PMUD QBAA QBUA QWTA

Arsenic (As) 1 - - - - - - -Beryllium (Be) 3 1 2 1 1 2 2

Boron (B) - - - 2 1 1 - -Manganese (Mn) 1 - - - 1 2 1 1

Selenium (Se) 1 - - - 1 - - -

Table A.21 : Percentage of samples exceeding health-based water quality criteria,by aquifer.

% exceedances of criteriaChemical PCCR PMDC PMNS PMUD QBAA QBUA QWTA

Arsenic (As) 6 - - - - - -Beryllium (Be) 19 100 17 5 2 2 10

Boron (B) 6 - 17 5 2 - -Manganese (Mn) 6 - - 5 4 8 5

Selenium (Se) 6 - - 5 - - -

Table A.22 : Number of samples exceeding non-health-based water quality criteria,by aquifer.

No. exceedances of criteriaChemical PCCR PMDC PMFL PMNS PMUD QBAA QBUA QWTA

Aluminum (Al) 5 1 1 6 2 8 - 5Chloride (Cl) - - - - 1 - - -Fluoride (F) 1 - - - - - - -

Iron (Fe) 6 1 1 5 10 27 7 13Lead (Pb) - 1 1 1 - 1 - -

Sulfate (SO4) 1 - - - - - - -



Table A.23 : Percentage of samples exceeding non-health-based water qualitycriteria, by aquifer.

% exceedances of criteriaChemical PCCR PMDC PMFL PMNS PMUD QBAA QBUA QWTA

Aluminum (Al) 31 100 100 50 10 15 - 24Chloride (Cl) - - - - 5 - - -Fluoride (F) 10 - - - - - - -

Iron (Fe) 38 100 100 42 50 52 58 62Lead (Pb) - 100 100 8 - 2 - -

Sulfate (SO4) 6 - - - - - - -

Table A.24 : Comparison of water quality data for Quaternary glacial drift aquifersfrom different literature sources for Northeast Minnesota. Concentrations representmedian values, in ug/L (ppb)1.

Chemical USGS AtlasHA-582

USGS AtlasHA-549

USGS AtlasHA-586

USGS AtlasHA-556

USGS AtlasHA-551

GWMAP

No. Samples 2 23 18 16 19 85Bicarbonate 141500 390000 159000 110000 277000 189000

Boron 30 20 60 40 60 18.25Calcium 29000 83000 38000 24000 58000 34432Chloride 900 4.9 2450 4800 3100 1160Fluoride 1000 300 200 200 300 310

Iron 270 550 190 460 280 501.65Magnesium 12500 25000 13000 7100 17000 10502Manganese 15 140 80 170 240 90

Nitrate 150 - 1200 - - 490pH 8 7.3 7.65 6.7 7.3 7.6

Potassium 1100 3600 2000 3500 3400 1430Silica - 21000 - 18000 20000 9449

Sodium 4950 15000 6350 4600 23000 4525Sulfate 9650 14000 15500 10000 14000 7290

Temperature - 10 - 10.5 12 8.1Total dissolved solids 142000 387000 179000 141000 354000 223000

Total phosphorus 10 - 40 - - 51

1 Temperature in degrees Celcius, and pH in pH units



Table A.25 : Comparison of water quality data for Precambrian bedrock aquifersfrom different literature sources for Northeastern Minnesota. Concentrationsrepresent median values, in ug/L (ppb)1.

Chemical EPA Report86-4033

USGS AtlasHA-549

USGS AtlasHA-586

USGS AtlasHA-556

USGS AtlasHA-551

GWMAP

No. of Samples 29 3 14 9 5 16

Bicarbonate 185000 433000 153500 150000 532000 135500

Boron 100 195 40 250 49

Calcium 41000 78000 30500 51000 110000 31747

Chloride 2500 2000 5500 8100 48000 3220

Fluoride 300 300 400 300 490

Iron 200 175 60 240 145

Manganese 80 45 80 380 103

Nitrate 1350 <500

Magnesium 10000 30000 9750 10000 39000 11780

pH 7.6 7.4 7.2 7.3 7.1

Potassium 1800 4700 1950 2800 5400 2007

Silica 22000 15000 19000 8733

Sodium 16000 16000 12500 9800 64000 8453

Sulfate 11000 7800 8150 13000 97000 9765

Temperature 9 10 14 7.7

Total dissolved solids 237000 379000 191500 235000 580000 194000

Total phosphorus 10 24

1 Temperature in degrees Celsius, and pH in pH units

Table A.26 : Comparison of water quality data for North Shore Volcanic aquifersfrom different literature sources for Northeast Minnesota. Concentrations representmedian values, in ug/L (ppb)1.

Chemical USGS Report94-4199

EPA Report 86-4033

USGS Report HA-582 GWMAP

No. samples 4 21 - 12Bicarbonate 48000 150 48000 119500

Boron - - 730 219Calcium 23500 45000 70000 23723Chloride 86800 47000 370000 2445

Conductivity 770.5 - - 270Fluoride 550 - 1200 715

Iron 33.5 - 90 204Magnesium 1950 9800 400 9555Manganese 17.5 - 30 35

Nitrate - - 600 <500pH 8.2 - 8.2 8.0




Chemical USGS Report94-4199

EPA Report 86-4033

USGS Report HA-582 GWMAP

Potassium 450 1300 950 674Sodium 65500 56000 200000 18686Sulfate 12200 14000 29000 9150

Temperature 8 - - 7.2Total dissolved solids 250500 351000 353000 172000

1 Specific Conductance in mmhos/cm, Temperature in degrees C, and pH in pH units.

Table A.27 : Summary of VOC detections for Region 1.

Unique No. Chemical Concentration Chemical class

1 toluene 0.3 BTEX1

2 toluene 0.2 BTEX3 chloroform 0.1 Trihalomethane4 toluene 0.2 BTEX5 dichlorodifluoromethane 1.3 Chlorofluorocarbon6 chloroform 0.7 Trihalomethane7 dichlorodifluoromethane 4.2 Chlorofluorocarbon8 dichlorodifluoromethane 13 Chlorofluorocarbon9 chloroform 0.8 Trihalomethane

10 dichlorodifluoromethane 0.6 Chlorofluorocarbon11 dichlorodifluoromethane 18 Chlorofluorocarbon12 toluene 0.3 BTEX13 chloroform 0.4 Trihalomethane14 toluene 0.3 BTEX15 chloroform 0.1 Trihalomethane15 dichlorodifluoromethane 0.9 Chlorofluorocarbon16 chloroform 3.5 Trihalomethane17 toluene 0.2 BTEX18 tetrachloroethene 0.3 Halogenated aliphatic19 chloroform 0.4 Trihalomethane20 toluene 0.3 BTEX20 chloroform 0.2 Trihalomethane21 toluene 0.2 BTEX22 benzene 0.2 BTEX23 tetrahydrofuran 10 Ether24 chloroform 0.7 Trihalomethane25 chloroform 0.3 Trihalomethane26 chloroform 0.7 Trihalomethane

1 BTEX refers to a class of VOCs which are aromatic, nonhalogenated, and frequentlyassociated with gasoline and fuel oils. Benzene (B), toluene (T), ethylbenzene (E), andxylene (X) are the most common of the BTEX compounds.



Appendix B - Figures

1. Location of Region 1.

2. Sample locations for the crystalline Precambrian aquifers.

3. Sample locations for the North Shore Volcanic aquifers.

4. Sample location for the undifferentiated Precambrian aquifers.

5. Sample locations for the surficial drift aquifers.

6. Sample locations for the buried drift aquifers.

7. Locations of VOC detections in Region 1.



Figure 1 : Location of Region 1.



Figure 2 : Sample locations for the crystalline Precambrian aquifers.



Figure 3 : Sample locations for the North Shore Volcanic aquifers.



Figure 4 : Sample location for the undifferentiated Precambrian aquifers.



Figure 5 : Sample locations for the surficial drift aquifers.



Figure 6 : Sample locations for the buried drift aquifers.



Figure 7 : Locations of VOC detections in Region 1.

Baseline Water Quality of Minnesota’s Principal Aquifers ...

Documents

Transcript of Baseline Water Quality of Minnesota’s Principal Aquifers ...